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PHYSICS

LAB MANUAL

2nd yearJunior High SchoolProf. James Tobin

Name: _________________________________________Group: __________________________________________

INDEXLAB PRACTICE

TITLE PAGE

Index 1Introduction 2Lab Schedule 3Rules for Entering the Laboratory 4Laboratory Precautions 5Science Lab Equipment 6

1 Straight Uniform Movement: Measuring Speed 102 Graphic Representation of Movement: Inclined to Roll 123 Sound 164 Free Fall 195 Friction Between Solids 226 Inertia 257 Newton’s 2nd Law 278 Newton’s Third Law 309 Transformations of Mechanical Energy 35

10 Pendulum Swing 3811 Magnetism 4012 Earth’s Magnetic Field 4313 Density of Solids 4514 Build Your Own Thermometer 4815 Heat Transfer 5116 Air and atmospheric pressure 5417 Density and Buoyancy 5918 Pascal and Archimedes 6319 Points of fusion and vaporization 6720 Electric conductivity 7021 Parallel and series circuits 7322 Constructing a Dimmer Switch 7523 Steadiness Tester 7824 Construction of an electromagnet 8025 Light and its Effects 8226 The Phenomena of Light: Looking at Images 8527 How Do Colors Mix? 8828 Construction of a Telescope 9029 Changing Colors 9330 Construction of a periscope 95

Bibliography 97

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Introduction

So you're asking, what is PHYSICS? Everything in the universe has an effect on every other thing. Physicists study those effects. Physics is a science that relates to all other sciences: Chemistry, Biology, Geology, Astronomy, Meteorology, Engineering, etc. If you can name it, chances are physics is involved.

Everything on Earth, everything in our solar system, everything in our galaxy, and everything in the universe moves and interacts, and forces play a big part in that. Physics studies those FORCES and interactions.

While physics has a remarkably large range of topics, it attempts only to describe those aspects of the world that can be dealt with by the SCIENTIFIC METHOD. It is not concerned with issues that cannot be verified even in principle, such as those studied in metaphysics.

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Lab Schedule

Lab Practice # Date123456789101112131415161718192021222324252627282930

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COLEGIO VILLA RICA

HIGH SCHOOL

RULES FOR ENTERING THE LABORATORY AREA

I. - All students must wear a long, regulation lab coat with name embroidered and bring the lab manual to enter the laboratory. If any student does not comply with this, he or she will receive the corresponding disciplinary sanction.

II.-Food or drinks are not allowed in the area.

III. - Discipline and order must be maintained within the laboratory.

IV. - Before beginning any labor, all material should be checked to verify its condition.

V. - Any student who breaks lab material will be required to replace it.

VI. - All instructions given by the lab instructor must be followed completely.

VII. - Check that all Bunsen burners are completely closed upon completing your lab work.

VIII. - All work areas should be clean before and after lab work is done.

IX. - No student is permitted to be in the laboratory without the authorization of the instructor.

X. - All students who do not comply with point number III of this set of rules will receive a discipline report and sanction. He or she will also lose the right to participate in laboratory studies for a month and the laboratory credit for that month.

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Laboratory Precautions

To avoid unnecessary accidents, and to indicate the action to be taken when an

accident occurs, read very carefully the following:

Safety Equipment

There is an emergency shower in each laboratory. Use it when corrosive liquids have spilled over clothes and skin.

If clothing is on fire, get the victim to the floor. The victim should be rolled over and over to smother the flames. Use a blanket or a lab coat.

Know the location of the fire extinguishers in the laboratory. Read the directions for their operation.

Small fires in test tubes, beakers and others can usually be smothered by covering with a heat resistant material.

Chemical burns must be washed promptly and thoroughly with water. It is the first treatment for all kind of accidents in which corrosive chemicals have been spilled or splashed on skin surfaces.

When a chemical substance has been splashed into the eyes, an immediate action must be taken to prevent damage to the sensitive tissues of that organ. The victim should wash the eyes with water for at least ten minutes. Seek medical attention immediately.

If possible, safety glasses or goggles must be worn during an experiment. Contact lenses won’t be permitted. Lab coats (buttoned) are necessary inside a laboratory. Use the appropriate color:

white.

Handling of Glassware

Accidents from the careless handling of glassware occur very frequently, however, they can be avoided observing the following rules:

before inserting a thermometer or glass tube into a stopper or rubber tube, be certain the hole is large enough to accommodate the glass, lubricate the glass and

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the rubber with glycerol, protect your hands by holding the stopper and the glass in towels, and grasp the glass close to the end that is to fit into the stopper and twist softly

Do not attempt to push or pull glass tubing or thermometers from rubber tubing, corks or stoppers which have become hardened. Cut the rubber or cork from the glass.

Do not try to force an oversized stopper into a flask or bottle. Try to use the proper size stopper always.

When a beaker is hot, use tongs and not your fingers. Never point test tubes at your neighbor or yourself when heating substances.

Handling of Chemicals

All bottles containing chemicals should be labeled. Volatile liquids such as alcohol, ether or benzene, must never be distilled or

evaporated near an open flame. Keep them well closed.

Waste All laboratory waste must be put in an appropriate container to avoid injuries to

third persons. Paper towels, corks, rubber stoppers, filter papers, etc., can be put in the regular

garbage after they have been cleaned of all chemicals

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Science Lab Equipment

You should know the name of each piece and its basic use.

For exact volume measurements of liquids. The pipette on the left is a Volumetric pipette. It has only one graduation for delivering one exact volume. Pipette on the right is a Mohr pipette. It has graduations for delivering any number of exact volumes.

Pipette

There are several styles of fillers used to draw liquids into a pipette. Physics’ students use a standard pipette bulb, described in lab techniques below.

Never draw a liquid into a pipette with your mouth.

Pipette filler

Used in conjunction with a vacuum connection to a water faucet to speed up filtration.

Filter flask

The Erlenmeyer flask is the most common flask in the physics’ lab. It is used to contain reaction solutions.

Erlenmeyer flask

The rounded bottom of the Florence flask makes it ideal for boiling liquids. It also makes this flask easy to tip over when sitting on the lab table.

Florence flaskThe volumetric flask is used to make solutions. It has a precise graduation line in the neck of the flask. A solute is placed into the flask, then the solvent..

Volumetric flask

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Beakers are the most versatile glassware in the lab and can be used for just about anything. The volume graduations on beakers should be used only for "ballpark" estimates.

BeakerUsed to make accurate measurements of liquid volumes. The bumper ring on larger cylinders is to prevent breakage if tipped over. Keep it near the top.

Graduated cylinder

This dish is used to recover dissolved solids by evaporation. While it can be heated, it should not be used for "strong" heating.

Evaporating dish A watch glass can be used like an evaporating dish for very small amounts of liquid. It can also be used to cover beakers.

Watch glass

When attached to the ring stand, this iron ring is used to support glassware above the lab table.

Support ring When attached to the ring stand, this clamp is used to hold a large test tube or Florence flask above the lab table.

Utility clamp

Crucibles are used as a container when something requires "strong" heating.

Crucible and coverThese tongs are used for picking up crucibles and crucible covers only.

Crucible tongs

Used as a support for beakers when placed across a support ring.

Wire gauzeUsed to light a lab burner. Not a toy noisemaker during lab.

Striker

Mortar and Pestle Test tube holder

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Used to grind solids into powers. Used to hold test tubes

for short periods of "gentle" heating.

When lined with filter paper, used to filter suspended solids from a liquid.

Filter funnel

Used for rinsing solids out of a container when filtering.

Wash bottle

Used to transfer solids from their original container to a scale for weighing.

Chemical spoon Used to close hoses by pinching them together.

Hose clamps

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COLEGIO VILLA RICAJR. HIGH SCHOOL

PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 1

STRAIGHT UNIFORM MOVEMENT: Measuring Speed

PREVIOUS INVESTIGATION

1. Movement can be defined as: ____________________________________________________

2. What part of Physics studies movement? ___________________________________________

3. What’s a moving object? ________________________________________________________

4. What’s the difference between distance and displacement? _______________________________________________________________________________

_______________________________________________________________________________

Mention three characteristics of the straight uniform movement:

a) ____________________________________________

b) ____________________________________________

c) ____________________________________________

INTRODUCTIONMotion is one of the key topics in physics. Everything in the universe moves. It might only be a small amount of movement and very very slow, but movement does happen. Don't forget that even if you appear to be standing still, the Earth is moving around the Sun, and the Sun is moving around our galaxy. The movement never stops. Motion is one part of what physicists call mechanics.

When we say a body is in movement, we interpret that its position is changing with respect to a fixed point.

The study of kinematics allows us to know and predict where a body will be found, what velocity it’ll have after a certain time or how long it’ll take to reach its destiny. To describe the movement of a body means establishing, at every instant, its position in space.

Simple and Complex MovementThere are two main ideas when you study mechanics. The first idea is that there are simple movements, such as if you're moving in a straight line, or if two objects are moving towards each other in a straight line. The simplest movement would be objects moving at constant velocity. Slightly more complicated studies would look at objects that speed up or slow down, where forces have to be acting.

There are also more complex movements when an object's direction is changing. These would involve curved movements such as circular motion, or the motion of a ball being thrown through the air. For such complex motions to occur, forces must also be acting, but at angles to the movement.

In order to really understand motion, you have to think about forces, acceleration, energy, work, and mass. These are all a part of mechanics.

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OBJECTIVE: Observe the characteristics of the straight uniform movement and calculate the speed of moving objects.

MATERIAL: masking tape, metric rulers, stopwatches, two or three wind-up toys per group

PROCEDURE:

1. Mark a measured distance on the lab bench with masking tape.2. Measure the time needed for each toy to travel the marked distance.3. Perform two more trials for each toy and record the results in the table.4. Calculate the average time for each toy.5. Use your results to calculate the speed of each toy.6. Obtain the speed between each point using the formula v = d/t where v is speed, d is distance

and t is time.

TOY #1 TOY #2

QUESTIONS.

1. What kind of movement did you observe? _______________________________________

2. For each trial, are you measuring instantaneous speed or average speed? _______________________________________

3. Why do you measure the time it takes for the toy to move three times? ______________________________________________________________________________________________________________________________________________________________________________________________________

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Trial # time( s)

distance ( cm )

speed( cm/s )

1

2

3

Trial # time( s)

distance ( cm )

speed( cm/s )

1

2

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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 2

GRAPHIC REPRESENTATION OF MOVEMENT: Inclined to Roll

ProblemHow does the steepness of a ramp affect how fast an object moves across the floor?

Skills Focusmeasuring, calculating, graphing

MaterialsSkateboard, meter stick flat board, about 1.5 m long, protractor, masking tape, small piece of sturdy cardboard, supports to prop up the board (books, boxes), 2 stopwatches

ProcedureReview the safety guidelines in Appendix A.1. You will record your results in the data table on the next page.

2. Lay the board flat on the floor. Using masking tape, mark a starting line in the middle of the board. Mark a finish line on the floor 1.5 m beyond one end of the board. Place a barrier after the finish line.

3. Prop up the other end of the board to make a slight incline. Use a protractor to measure the angle that the board makes with the ground. Record the angle in your data table.

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4. Working in groups of three, have one person hold the skateboard so that its front wheels are even with the starting line. As the holder releases the skateboard, the other two students should start their stopwatches.

5. One timer should stop his or her stopwatch when the front wheels of the skateboard reach the end of the incline.

6. The second timer should stop his or her stopwatch when the front wheels reach the finish line. Record the times to the bottom of the ramp and to the finish line in the columns labeled Time 1 and Time 2.

7. Repeat Steps 4–6 two more times. If your results for the three times aren’t within 0.2 seconds of one another, carry out more trials.

8. Repeat Steps 3–7 four more times, making the ramp gradually steeper each time.

9. For each angle of the incline, complete the following calculations and record them in your data table.

a. Find the average time the skateboard takes to get to the bottom of the ramp(Time1).b. Find the average time the skateboard takes to get to the finish line (Time 2).c. Subtract the average Time 1 from the average Time 2.

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Data TableComplete the data table below.

Analyze and ConcludeWrite your answers in the space provided.1. Calculating How can you find the average speed of the skateboard across the floor for each angle of incline? Determine the average speed for each angle and record it in your data table.__________________________________________________________________________________________________________________________________________2. Classifying Which is your manipulated variable and which is your responding variable in this experiment? Explain. (For a discussion of manipulated and responding variables, see the Skills Handbook.)__________________________________________________________________________________________________________________________________________

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Angle (degrees)

Trial Number

Time 1 (to bottom) (s)

Time 2 (to finish) (s)

Avg Time 1 (s)

Avg Time 2 (s)

Avg Time 2 – Avg Time 1 (s)

Avg Speed (m/s)

123123123123123

3. Graphing On a graph, plot the speed of the skateboard (on the y-axis) against the angle of the ramp (on the x-axis). Connect the points on your graph. Use the space below to make your graph.

4. Drawing Conclusions What does the shape of your graph show about the relationship between the skateboard's speed and the angle of the ramp?__________________________________________________________________________________________________________________________________________5. Measuring If your measurements for distance, time, or angle were inaccurate, how would your results have been affected?__________________________________________________________________________________________________________________________________________6. CommunicatingDo you think your method of timing was accurate? ____________________________Did the timers start and stop their stopwatches exactly at the appropriate points? ____ How could the accuracy of the timing be improved?Write a brief procedure for your method._________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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´


PHYSICS LABORATORY

Name:______________________________Date:________________Group:__________________

LAB PRACTICE # 3Sound

Previous investigation : Make a list of objects in which their vibrations make sound. Why does this happen?

Objective: To observe the propagation of sound waves in the air and in water and their characteristics.

General information : A sound is the product of a wave motion that travels by way of a medium such as air, water or brass. The wave is a vibration with a movement that goes from one side of the node line to another. The node line is a wave's position of equilibrium. The amplitude of a wave is the maximum distance that separates the crest from the node line. In a vibration the particles do not all vibrate at the same time, but each one has its own state of vibration in a given moment, each one has its own phase.

Experiment 1

Material : 2 tuning forks 1 container with water 8 tall glasses (same size) 1 metal teaspoon Balloons Cork A clock

Procedure : 1. Place the cork on the surface of the water. 2. Vibrate the tuning fork and place it into the container. 3. Observe the water and the cork. What type of movement do you observe on the surface and in the cork? __

------------------------------------------------------------------------------------------------------------------------------------___ Experiment 2

Procedure : 1. Hold the tuning fork in vertical position on the table. 2. Make the other tuning fork vibrate and place it in the same position as the other, at a distance of 20cm. What happens to the first tuning fork?

_----------------------------------------------------------------------------------------------------------------------------------Through what does the sound propagate?

-----------------------------------------------------------------------------------------------------------------------------------Where does sound propagate best?

------------------------------------------------------------------------------------------------------------------------------------

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Experiment 3

Procedure: In each activity, do what is indicated; take note if you hear any sounds and describe them.

A) Stretch a rubber band with your hands and cause it to vibrate by plucking it.

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B) Take the tuning fork. Place it behind of your ear and listen.

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C) Strike the tuning fork smoothly against something hard. Maintain it 15 cm from your ear and listen.

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D) Place your ear against the table and ask a classmate to touch the table with the tip of the tuning fork while it is vibrating.

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E) Blow the balloon up to medium size. Place the clock against one of the sides of the balloon and your ear against the other side.

----------------------------------------------------------------------------------------------------------------------------------------------------

F) Place the tall glasses in rows, separated from each other by 5 cm..

----------------------------------------------------------------------------------------------------------------------------------------------------

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1. Fill them with water beginning with a little in the first one and a little more in each glass until the last one is full.

2. Strike the first glass with the teaspoon below the water level to verify that the notes of the musical scale are produced by putting or removing water.

3. Repeat the operation with the remaining glasses, until each glass resembles each one of the notes of the musical scale.

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COLEGIO VILLA RICA

JR. HIGH SCHOOL PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 4FREE FALL


1. What were Aristoteles´ ideas about free fall? ____________________________

2. Describe the development of the experiment that Galileo performed at the Tower of Pisa:

3. What were Galileo´s conclusions? __________________________________________

-Draw (illustrate) Issac Newton´s experiment that was performed to prove Galileo´s free fall conclusions.

INTRODUCTION

It´s very common for any of us to observe how bodies fall over the Earth´s surface, such as when a leaf or a dry branch fall from a tree to the ground, or when a ball, marble, stone, etc. fall over the Earth´s surface. But, what causes these bodies to fall? Which falls faster…a heavier body or a lighter body if we ignore the resistance caused by air friction and if they´re dropped from the same height?

When a body falls towards the Earth´s surface and the effect of air resistance over that body is practically nonexistant, then we say it is in free fall.

In free fall, all bodies begin with an initial velocity of zero and acquire a velocity that increases as time goes by. There´s a change in velocity in all bodies when they fall. This acceleration is caused by the attraction that the Earth has over all bodies and is called acceleration by gravity.

Place Gravity valueSea level 9.81 m/s2

Distrito Federal 9.78 m/s2

North Pole 9.83 m/s2

Ecuador 9.78 m/s

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OBJECTIVE

Analyze free fall and identify it as a uniformed and accelerated movement.

MATERIAL:

A tape measurePaper sheets2 empty match boxesA timerCoinsA thick book or notebook

PROCEDURE:

1. Choose a classmate that will stand in a chair and have him/her place his/her arms at shoulder height. He/she will drop a paper sheet from his/her hand and from the other hand he´ll drop a paper sheet that has been crunched into a ball shape

Which one reached the ground first? _____________________________________________________

Why did the flat paper sheet take a longer time to reach the ground? ________________________________

2.-Fill a match box with coins and keep the other one empty. Perform the experiment once again. From one hand, you’ll drop the empty box and from the other the one that has coins inside.

-Which one has more mass?__________________________________

- Which one reached the ground first?___________________________________

-What’s the importance of mass in the free fall of bodies?____________________________________

3. Place the flat paper sheet over the book and let them fall from the same height.

Did they fall together? ___________________________________________________

-Why?_______________________________

4. Drop a coin from the 3 different heights that are indicated in the chart. Measure the time it takes to free fall and touch the ground. Register this data and calculate the final velocity using this formula:

V =g · t (gravity = 9.8 m/s2)

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coin height time velocity

Test 1 1.5 m

Test 2 2.0 m

Test 3 2.5 m

QUESTIONS

Underline the right answer.

1. The coin’s velocity in all 3 cases was:a) the same b) greater c) different d) less

2. The acceleration by gravity is a ___________ magnitude:a) Scalar b) Colineal c) Vectorial d) Supplementary

3. The vector of acceleration in free fall is directed towards:

a) the south of the Earth

b) the center of the Earth

c) the north of the Earth

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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 5FRICTION BETWEEN SOLIDS


1. Define friction: __________________________________________________________________

2. What’s the difference between static friction and dynamic (moving) friction? ______________________________________________________________________________________________________________________________________________________________

4. Mention three advantages of friction. ______________________________________________________________________________________________________________________________________________________________

5. Mention three disadvantages of friction. ______________________________________________________________________________________________________________________________________________________________

INTRODUCTION

Friction is a force that happens when two bodies move against each other in opposite directions.

Many times, when we pull or push an object it doesn’t move because another force acts on it too; this force appears every time an object that is in contact with another moves.

This rubbing is due to rough extensions or small lumps that exist on the surfaces that are in contact, which is why the smoother the surfaces are, the less friction will exist between them.

Friction produces two main effects: heat and wear. Thanks to this, cavemen were able to make fire, by rubbing sticks. Now, thanks to the friction on a match’s head, modern man can also obtain fire.

When a car moves the friction force appears between its tires and the street, and also between the air and the car. The friction between the tire’s rubber and the asphalt represents a positive aspect of friction because it allows the car to move with control of movement while driving on the highway.

However, the friction between the air and the car opposes its movement which is why cars are made with an aerodynamic design so that they can minimize the air’s resistance.

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OBJECTIVE:

Observe that friction force opposes movement.

MATERIAL:

A bookRubber bandsSpring scaleMetal or wooden cylinders: pencils, broom pieces, markers or tubes.

PROCEDURE:

1.-Place a rubber band around a book and attach a spring scale to it. Then place it over a smooth surface.

2.-Slowly pull from the book in order to begin movement.

3.-Register the scale’s reading just a moment before it moves.

4.-Now that movement has begun, try to make it move uniformly, this means with constant speed and register the scale’s reading.

5.-Repeat the previous operations, but now place the book over the cylinders.

force Book that slides Book that rolls

Force to begin movement(N)

Force during movement (N)

Force Force Force Force

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QUESTIONS.

1. Comparing the obtained values: is more force required to begin movement or to maintain it? _______________________________________________________________________________

2. What is friction? ________________________________________________________________

3. What’s the name of the friction that has to be defeated in order to begin movement?_____________________________________________________________________

4. What’s the name of the friction that exists during movement? ___________________________

5. What type of friction is greater: that which happens when an object is sliding or when it’s rolling? ______________________________________________________________________________

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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 6INERTIA


1. When are you affected by inertia: when you’re sitting still or when you’re moving? _____________________

2. How are mass and inertia related? ________________________________________________

3. How did Newton define “mass”? __________________________________________________

4. What is the mass unit in the SI? __________________________________________________

5. Why is it good to use seat belts?__________________________________________________

INTRODUCTION

Inertia is the resistance of any physical object to a change in its state of motion.The property of inertia is related to the mass of a body. The greater the mass, the greater is the inertia of body. Thus, a lighter body has less inertia than a heavier body. If the mass of the body is more, it is more difficult to move the body from rest. It is also more difficult to change the speed and direction of motion of a moving body. Thus mass is a measure of inertia.There are 2 types of inertia, inertia of rest and inertia of motion.Inertia of rest : If a body is at rest, it will continue to remain at rest unless an external force is applied to change its state of rest.Inertia of motion: A body which is in the state of motion has inertia of motion and it continues to be in the state of motion with the same speed in the same direction in a straight line unless an external force is applied on it to change its state.An example of inertia occurs when a passenger in a running bus leans forward when the bus stops suddenly. When the bus is running, the whole body of the passenger is in the state of motion. When the bus stops, the lower part of the passenger’s body which is in contact with the bus, comes to rest. But the passenger’s upper portion remains in the state of motion due to the inertia of motion.

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OBJECTIVE: Observe the property of inertia.

Experiment 1: What Changes Motion?

Materials: heavy book, metal washers, toy car

Procedure:

1. Stack several metal washers on top of a toy car.2. Place a heavy book on the floor near the car.3. Predict what will happen to both the car and the washers if you roll the car into the book.4. Test your prediction.

Think It Over:

1. What happened to the car when it hit the book? ________________________________________________________________________

2. What happened to the washers? ________________________________________________________________________

3. What might be the reason for any difference between the motions of the car and the washers? ________________________________________________________________________

Experiment 2: Around and Around: An object moving in a circle has inertia.

Materials: masking or cellophane tape, table tennis ball, thread

Procedure:

1. Tape one end of a length of thread (about 1 m) to a table tennis ball.2. Suspend the ball in front of you and swing it in a horizontal circle, keeping it 2–3 cm above

the floor.3. Let go of the thread and observe the direction in which the ball rolls.

Think It Over:

1. At what point do you need to let go of the thread if you want the ball to roll directly away from you? ________________________________________________________________________

2. Toward you? ________________________________________________________________________

3. Draw a diagram as part of your answer.

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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 7NEWTON´S 2nd LAW


1. Define “force”:_______________________________________________________

2. Define “acceleration”: __________________________________________________

3. What is the mathematical expression for Newton’s 2nd Law?

4. What formula is used to calculate acceleration if the magnitudes involved are distance and time?

INTRODUCTION

Daily we see cars increasing and decreasing in speed or changing direction. These changes are called acceleration and these movements of acceleration are due to applied forces.

The effect of such forces can be produced by only one force called net force or resulting force. This net force applied over the body can cause acceleration. The relationship between the net force and the acceleration is established by Newton’s 2nd Law.

When you want to quickly move a heavy box, you ask a friend to help you, which means you’ll increase the force. When the force increases, acceleration also increases.

If a Volkswagen and a bus are pushed using the same force, the Volkswagen will accelerate a lot more. The lesser mass the body has, the greater the acceleration will be if the same amount of force is applied.

If force is applied to a 2 kg mass and produces an acceleration of 4 m/s 2; then when we apply that same force to a 1 kg mass it will produce an acceleration of 8 m/s2. Acceleration is inversely proportional to the mass.

These are examples of what Newton’s 2nd law establishes: “The acceleration that a body goes through or experiments, is directly proportional to the force that acts over it and inversely proportional to the mass”

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OBJECTIVE

Prove Newton’s 2nd Law with an experiment: the relationship between force, mass and acceleration.

MATERIAL:

Small carVarious sized massesPulleyStringBaseTimer or watch with second hand.

PROCEDURE:

1. Put together a device as shown in the pictures. Load the car with masses and use another mass to cause the acceleration.

2. Measure a 1 meter distance (starting from the table’s edge) and mark this distance.3. Load the car with the masses and attach the other mass on the opposite end of the string to cause the accelerated movement. 4. Using your watch or timer, measure the time it takes travel the 1 meter distance.

Important: Remember that when the movement begins the car is still and the initial velocity is 0.

5. Repeat this last step two more times, increasing the mass each time.

6. Register the obtained values.

7. Calculate the acceleration.

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distance time acceleration a = 2d / t2

Car with a total mass of _______g



QUESTIONS:1. In which case was a greater acceleration obtained? ______________________________________

2. Why? _______________________________________________________________

3. What is the mathematical expression for Newton’s 2nd Law?

4. Write down Newton’s 2nd Law: _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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COLEGIO VILLA RICA JR HIGH SCHOOL

PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 8NEWTON´S THIRD LAW.


1. What other name does Newton’s 3rd law receive? ____________________________________________________________________________

2. Why does your hand hurt if you hit a wall? ____________________________________________________________________________

3. How can a rocket be launched out of the atmosphere? ____________________________________________________________________________

____________________________________________________________________________

4. Why do people experiment a backwards movement when a gun is fired? ___________________________________________________________________________

____________________________________________________________________________

INTRODUCTION

Some forces are the result of interactions in which the objects have physical contact, like friction force; and others are the result of interactions to distance, like the force of attraction due to gravity.

Newton discovered a very important characteristic in all interactions; he discovered that every time an object A interacts with an object B, each one of them exercises a force over the other. This is why, for example, when you apply a force to stretch a spring, the spring pulls you.

These two forces are known as action and reaction. Forces always appear in pairs. A force doesn’t exist if there’s not another force with the same magnitude and direction as the first one, but moving in an opposite direction. It’s important to mention that the action and reaction forces are always applied to two different bodies and are exercised simultaneously.

Newton expressed this fact in his 3rd Law: “For every action force there is an equal but opposite reaction force”.

Newton’s 3rd Law helps us understand why a fish can swim moving its tail or why a bird can fly flapping its wings.

OBJECTIVE: Observe the action-reaction forces of Newton’s 3rd Law.

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MATERIAL:

A ruler that’s divided in cmA strawScissorsStringBalloonScotch tape2 stools

PROCEDURE:

1. Put together a device like the one shown in the drawing below.

2. Cut a 10 cm piece of straw and 5 meters of string.

3. Place the thread in the straw.

4. Place the stools 4 meters apart.

5. Tie tightly one end of the string to the one leg of each of the stools.

6. Inflate the balloon and hold it so the air cannot escape. Do not tie it.

7. Attach the inflated balloon to the straw using scotch tape.

8. Let go of the balloon and watch what happens.

9. Mark down in the figure which is the action force and which is the reaction force, their directions an over which body each acts.

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QUESTIONS:

1. What did you observe? ______________________________________________________________________________________________________________________________________________________________

2. Write down the action and reaction law: __________________________________________

____________________________________________________________________________

3. Look at the following examples and write down what force acts on each body.

Shooting a cannonball from a cannon.

Action:________________________________

Reaction:______________________________

The launching of a rocket.

Action:________________________________

Reaction:______________________________

A diver’s jump.

Action:________________________________

Reaction:______________________________

Activity 2

1.1. Roll the sheet of paper into a cone. Fasten the ends.

2. In each corner of the Styrofoam carefully make a hole 2 cm from the edge using a pencil. Then make a hole in the center of the Styrofoam.

3. Pass the thread through the center of the Styrofoam sheet and the cone so that it enters the base and exits the cone. The base of the cone should be on the Styrofoam with the point facing upwards. If the hole in the cone is too small, cut it so the thread will move through it freely.

4. Make several small cuts in the base of the cone in order to form tabs and glue or tape them to the sheet of Styrofoam.

5. Place a balloon in each of the holes in the corners with the valves under the sheet.

6. Tape the balloons to the sheet being careful not to cover the valves.

7. Place the string in a vertical position and check that the “rocket” is free to move.

8. Place small pieces of Styrofoam or paper under the rocket.

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9. Inflate the balloons and hold them so the air does not escape. You will require more than one person to help hold the balloons.

10. Release the balloons at the same time and observe.

11. Repeat the procedure again from step 8 but only inflate 2 balloons (use 2 balloons that are in opposite corners from each other).

QUESTIONS

1. When the balloons were released, what moved the small pieces of paper or styrofoam under the rocket? In what direction was the force moving that affected the small pieces?

____________________________________________________________________________

____________________________________________________________________________

2. As you will remember, a force is needed to modify the movement of an object. What force caused the rocket to move upwards? Where did it come from?

____________________________________________________________________________

____________________________________________________________________________

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3. Compare the velocity of the rocket when it was propelled by 4 balloons and when it was propelled by only 2 balloons. How does force affect propulsion?

____________________________________________________________________________

____________________________________________________________________________

4. The magnitude of the force affecting the small pieces of Styrofoam and the force propelling the rocket are the same. Why?

____________________________________________________________________________

____________________________________________________________________________

5. Explain the movement of the rocket based upon Newton’s Third Law of Motion.

____________________________________________________________________________

____________________________________________________________________________

COLEGIO VILLA RICA

JR HIGH SCHOOL

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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:___________________

LAB PRACTICE # 9 Transformations of Mechanical Energy


1. Define “energy”______________________________________________________2. Investigate where these energy sources are obtained from.

a) Geothermic energy _____________________________________________________

b) Eolic energy_________________________________________________________

c) Radiant energy________________________________________________________

d) Atomic energy________________________________________________________

e) Hydraulic energy_______________________________________________________

INTRODUCTION

We can find energy in all bodies, in the smallest part of matter and in the biggest bodies that perform a job. The capacity that allows all bodies to perform a job is called energy.

For science, energy is the scalar common to all forms of matter that are found in nature and it only manifests itself when it passes from one body to an other…when it´s transformed.

In our daily lives, we often talk about work and energy, like when we talk about the importance of eating right and resting so that our bodies have energy to work.

Energy has always been related to the everyday chores of human beings. In the old times men did their chores by using their bodies´energy. Then they learned to domesticate animals and they used their energy to make their jobs easier. Later on, they discovered other sources of energy and they learned how to use the wind to make their ships sail and how to use the water’s current to move their mills.

People have learned a lot more about science and technology and new energy sources have been discovered, which is why now our daily chores can be done in an easier way and our life quality has improved.

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OBJECTIVE:

Learn about the different manifestations of energy.

MATERIAL:

2 m of ½ inch transparent plastic hose A steel ball that can move freely in the hose. A piece of resistant wire or string.

Pliers Tape measure or ruler

PROCEDURE:

1. Bend the hose into a circle of about 30 cm in diameter as shown but do not pinch it or twist it. Tie it together where it crosses itself as shown.

2.. Check that the steel ball is able to roll freely in the hose.

3. Keep the curved hose in a vertical position and let the longest end extend over the tables surface.

4. Raise the free end of the hose 10 cm and drop the ball into the hose. Observe and note your observations.

5. Raise the free end of the hose an additional 5 cm and release the steel ball again. Observe its movement and mark its maximum height.

6. Repeat the procedure again but increase the height by 5 cm each time until the steel ball is able to pass through the curve.

QUESTIONS

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1. What happened the first time you released the steel ball? Describe the type of movement it experienced in each section of the hose. What height did it reach?

____________________________________________________________________________

____________________________________________________________________________

2. On the second attempt, was the ball able to pass over the curve? What height did it reach? How was its speed compared to that which it reached in step 4?

____________________________________________________________________________

____________________________________________________________________________

3. Complete the following table based on your observations

Height of release(cm) Height the steel ball reached (cm) Did the ball pass the curve?

10

15

20

25

30

35

40

45

4. What is the relation between height released and maximum speed achieved?

____________________________________________________________________________

5. What is the relation between maximum speed achieved and height reached in the curve?

____________________________________________________________________________

6. What was needed in order for the ball to pass over the curve?

____________________________________________________________________________

7. Explain your previous answers based on the Law of Conservation of Energy.

____________________________________________________________________________


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PHYSICS LABORATORY

LAB PRACTICE # 10Pendulum Swing

Previous Investigation:

1. Define kinetic energy. __________________________________________________________________

2. Define potential energy. __________________________________________________________________

Energy Around Us

We use the concept of energy to help us describe how and why things behave the way they do. We talk about solar energy, nuclear energy, electrical energy, chemical energy, etc. If you apply a force to an object, you may change its energy. That energy must be used to do work, or accelerate, an object. We also speak of kinetic energy, potential energy, and energy in springs. Energy is not something you can hold or touch. It is just another means of helping us to understand the world around us. Scientists measure energy in units called joules.

Active Energy vs. Stored Energy

Kinetic and potential energies are found in all objects. If an object is moving, it is said to have kinetic energy (KE). Potential energy (PE) is energy that is "stored" because of the position and/or arrangement of the object. The classic example of potential energy is to pick up a brick. When it's on the ground, the brick had a certain amount of energy. When you pick it up, you apply force and lift the object. You did work. That work added energy to the brick. Once the brick is in a higher/new position, we would say that the increased energy was stored in the brick as PE. Now the brick can do something it couldn't do before; it can fall. And in falling, can exert forces and do work on other objects.

Skills Focus: Observing

Materials:

washers or rubber stoppers, string, ring stand, 2 clamps, meter stick

Procedure:

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1. Set up a pendulum using washers or a rubber stopper, string, a ring stand, and a clamp.2. Pull the pendulum back so that it makes a 45° angle with the vertical. Measure the height of

the stopper. Release it and observe how high it swings.3. Use a second clamp to reduce the length of the pendulum as shown. The pendulum will run

into the second clamp at the bottom of its swing.4. Pull the pendulum back to the same height as you did the first time. Predict how high the

pendulum will swing. Then set it in motion and observe.5. Add additional mass to the pendulum and observe its motion.

Observing:

1. How high did the pendulum swing in step #2? ___________________________________ 2. How high did the pendulum swing in step #4 (when the second clamp was in place)?

___________________________________3. Was the original amount of potential energy affected by changing the length of the

pendulum in mid-swing? ________________________4. How did the change in mass affect the swing of the pendulum?

______________________________________________________________________5. Where does the pendulum have the greatest potential energy?

______________________________________________________________________6. Where does the pendulum have the greatest kinetic energy?

______________________________________________________________________


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PHYSICS LABORATORY

Name:_________________________________ Date:__________________ Group:__________

LAB PRACTICE # 11Magnetism

Previous investigation: What is magnetism? ______________________________________________________________________________________________________________________________________________________________

Objective : To observe the properties of a magnet; to predict and to observe the effects of the magnetic fields of the poles of a magnet and to build a compass.

General information: The first magnetic phenomena observed were associated with magnetite, a mineral found in the old city of Magnesia, a region of Asia Smaller. In a natural way, this stone attracts ferrous materials, a fact that is known as magnetism. Magnetism is the property that magnets have to attract iron, nickel, and cobalt.

MATERIALS:An iron or steel barA hammerA compassIron filingsA piece of paperA bar magnet

PROCEDURE:

Activity 1

1.- Firmly hold the iron bar in your hand and hit it with the hammer. Be careful not to hit your hand. Place the bar next to the iron filings to see if they are attracted.

2.- Repeat step 1 but place the bar in different positions: horizontal, vertical, inclined, to the right, etc. What do you observe?

3.- Place the compass in a level place, far from magnets or iron objects and leave it until it points North. Place the iron bar so that it is parallel to the compass needle, that is to say, North-South.Change the angle of the bar and see what happens.

4.- Place the compass in a vertical position, as shown in the picture, inclining it until it is again parallel to the compass needle. Place the bar parallel to the needle and change the angle of the bar. What do you observe?

5.- Hit the bar again with the hammer on one of its ends and bring it close to the iron filings again. What do you observe?

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QUESTIONS:

1.What happened the first times that you hit the bar with the hammer?

____________________________________________________________________________

2. The iron bar is made up of a great many magnetized particles called magnetic domains. What is the relationship between them and the magnetic properties of an object? ____________________________________________________________________________

____________________________________________________________________________

3. If it is possible to magnetize an object by hitting it, then what will happen to a temporary magnet that has become magnetized by rubbing it against a permanent magnet?

____________________________________________________________________________

____________________________________________________________________________

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Experiment 2

Prococedure:- Place the magnet on the table and cover it with the sheet of paper. - Spread the iron filings on the sheet of paper. - Observe how the filings are grouped. - Illustrate how the iron filings were accommodated.

Answer the following:

a) The points where the greater quantity of filings accumulated were at the extremes of the _________ and said points receive the name of ___________________________poles.b) In the mid- parts of the bar, lines are formed that are known as _____________________c) The space that surrounds a magnet and where its force is located is called: ___________________

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