Ocean Science!• Monday

– Review 20-2 reading guide questions.– Review for tomorrow’s quiz– Start frozen seas video

• Tuesday– 20-2 Ocean Life Quiz

• Wednesday– Research questions– Finish Frozen seas video

• Thursday– Ocean resources

• Friday– Ocean Resources

Improvements • Needs reordered according to gravity notes for real.

• Yes, definitely needs reordered

• Look up common misconceptions & address them

• Use physics website more!

• More on weight…students never get how to calculate weight! Is important later too.

• Weight on other planets!

• Make peanut butter jars with different weights for different gravity!

• It’d be coolest if it were a regular weight on Earth!

Bonus!

• The acceleration due to gravity on the “surface” of Jupiter is 25.9 m/s2. How many pounds would a 80.0 kg person weigh there?

(1.00 lb = 4.46 N)

Bell Work 4/8/13

New Bell Work Sheet!

1. How many Newtons would a 885.0 kg object weigh on Earth’s surface? (Use F = ma, a = 9.81 m/s2)

2. Convert this to lbs.

Bell Work 4/22

1. A 45.0 kg ball experiences a force of 441.45 N. What will it’s acceleration be?

2. A 90.0 kg ball experiences a force of 882.9 N. What will it’s acceleration be?

3. W5SAYWoS

Schedule • Wednesday – Update grades– See quizzes?– Review labs– Law of gravity notes!

• Thursday– Law of gravity notes!

• Turn in your newton’s laws demos lab!

• Make sure your grade sheet update! Show me for some pts!!! 10 pts!!!!!

Today you are going to…

take notes on gravity!

So you can…

explain what affects the force of gravity & predict the gravity between different objects

You’ll know you’ve got it when you can • Answer the questions at the end of slide show

The 4 Fundamental Forces

Gravity!

• What does it do?– Holds objects on Earth– Makes objects fall– Keeps satellites in orbit!

Gravity!

• Gravity is the attraction between any two objects that have mass.

• It’s actually the weakest force!

• It’s magic!!– We don’t really understand it (but then, that’s

true of most fundamental stuff)

• Sir Issac Newton wrote the law of universal gravitation.

Gravity & Mass

• Universal gravitation equation G = 6.67 x 10-11

• 2 things affect the force of gravity: ___________ and _____________

• The force of gravity is ___________________ related to mass.

Gravity & Mass• Gravity is the attraction between any two objects that

have mass. Why don’t we notice the force of gravity between all objects?

6.67 x 10-11 (50 kg)(5.97 x 1024 kg) (6,371,000 m)2

491 N = 110 lbs

6.67 x 10-11 (50 kg)(1.0 kg) (1 m)2

3.35 x 10-9 N 0.000 000 003 35 N = 0.000 000 000 754 lb

• Gravity is the attraction between any two objects that have mass. Why don’t we notice the force of gravity between all objects?

Even though the force of gravity between less massive objects is, it would be noticeable if it were the only force around.

However, on Earth the gravity of Earth overpowers these other gravities, not to mention the fact that the gravity between you & other objects are pulling in all sorts of directions, so they cancel out.

Far away from planets, the gravity of semi large objects would have an effect. It’s one way we could deflect an oncoming asteroid!

Gravity & Distance

• Universal gravitation equation G = 6.67 x 10-11

• The force of gravity is ___________________ related to distance.

Gravity & Distance

• The force of magnetism

• Which is stronger, gravity or magnetism?

• How are gravity and magnetism similar?

• How are gravity and magnetism different?

Gravity, Mass, & Distance

What happens to the force of gravity if:

mass doubles?

distance doubles?

So gravity depends more on ___.

What’s this table tell you?

• Would your mass or weight be any different on the moon? Why?

• Would your mass or weight be any different on the top of a tall mountain? Why?

• What is the weakest fundamental force?• Who discovered the law of gravity?• What 2 things does the force of gravity depend on?• Which does it depend on more?• The force of gravity is directly related to ___, and you

can tell because ____• The force of gravity is directly related to ___, and you

can tell because ____• You would weigh ___ on the moon because _____.• You would weigh ___ on Mt. Everest because _____.

Today you are going to…

take notes on weight & freefall

So you can…

calculate weight

explain how objects freefall

explain the behavior of projectiles

You’ll know you’ve got it when you can • Answer the questions at the end

Bell Work 5/5/14

Do 1-7 on the Gravity and Projectile Motion Study Guide #1

Free Fallin’ Tom Petty https://www.youtube.com/watch?v=jVa0sISCjXc

Freefall!

• Freefall - when gravity is the only force acting on an object.

• All things on Earth’s surface fall with same acceleration (_______).

• If 2 objects were both dropped from the same height, they would hit the ground at the same time. Why don’t we notice this?

• Strobe light & drops of water!

Air Resistance!

• Air resistance keeps all objects from falling with the same acceleration on Earth.

• Terminal velocity – the fastest an object can fall due to air resistance– Happens when force of air resistance = weight

• FNET = 0, therefore a = _______!

• Moon Hammer Drop

• Feather in vacuum

• Elephant and feather on physics classroom

7 Minutes of Terror• Landing

– 13,000 mph to 0 mph in 7 min• https://www.youtube.com/watch?v=Ki_Af_o9Q9s

• What are some differences between Earth and Mars that

affect how things

fall there?

• Jill and Nick have a task. They both have to push a cart down the hall with an acceleration of 5.0 m/s2.

• Jill’s cart has a mass of 10.0 kg. How hard does she have to push it?

• Nick’s cart has a mass of 20.0 kg. How hard does she have to push it?

• Even though Nick pushes his cart twice as hard, his cart accelerates at the same rate because…

Freefall! • Why do all things fall with the same acceleration?

Shouldn’t heavier objects fall faster?• Earth’s force of gravity on an object is its weight.• On the surface of Earth: 1.0 kg weighs about 9.81 Newtons.

• A 5.0 kg object weighs 44.05 Newtons. Calculate its

acceleration when dropped.

• A 10.0 kg object weighs 98.1 Newtons. Calculate its acceleration.

Why is the acceleration for everything the same?

• If something has twice the weight, it also has twice the inertia, therefore it’s twice as hard to accelerate.

• Gravity is like horse drawn carriages, or a bunch of tiny magnets!

• Would two pieces of clay fall faster if combined?

Bell Work 4/25/13

1. What 2 things determine the strength of the force of gravity?

2. Do all objects fall with the same acceleration on Earth’s surface? Why/Why not?

3. Do objects with twice the weight fall with the same acceleration? Why/Why not?

4. Which falls faster, a bullet that’s fired horizontally or a bullet that’s dropped? (or neither)

Weight

Weight Weight don’t tell me!• Weight - force of gravity between an object &

a planet.

• FW = ma (a is acceleration due to gravity)

• How much would a 1.00 kg object weigh on the surface of Earth? In lbs?

Today you are going to…take notes on projectiles and circular motion.

So you can…predict and explain the motion of projectiles & objects in circular motion

You’ll know you’ve got it when you can • Accurately answer the questions

Schedule Monday Gravity Notes & Questions

Tuesday

Projectile & Circular Motion Notes & Questions

WednesdayOrbits!

ThursdayReview Questions & Begin Egg Drop Project

Friday

Build Egg Drop Project

7 Minutes of Terror• Landing

– 13,000 mph to 0 mph in 7 min• https://www.youtube.com/watch?v=Ki_Af_o9Q9s

• What are some differences between Earth and Mars that

affect how things

fall there?

Free Fall & Reaction Time

• http://www.brianmac.co.uk/rulerdrop.htm

Projectile Motion

Projectile Motion

• Projectile motion – motion in which an object (projectile) is thrown near a planet’s surface, and gravity is the only force acting on it– Ex. Thrown football, bullet shot, cow launched

from catapult.

• Projectiles follow curved path called a parabola.

Projectile Motion

• Projectiles are in freefall!

Projectile Motion• has horizontal (left & right) & vertical (up & down)

motion. • The horizontal and vertical motion are

independent. – They don’t affect each other!

• Which will hit the ground first, a bullet fired from a gun or a bullet dropped from the same height?

• Mythbusters!!• http://www.youtube.com/watch?v=D9wQVIEdKh8

Horizontal Projectile Motion

• The horizontal (Vx) velocity of a projectile doesn’t change!– This makes sense because the net force in that

direction is ____________.

Vertical Projectile Motion

• A projectile– takes as long to go up as it does to come down

to the same point at which you released it. – It will be going the same speed in the opposite

direction when it reaches its original height.– At its maximum height:

• vy =

• t =

Projectile Motion• What 2 things affect the distance of a

projectile?

• What angle will launch a projectile farthest?

• What angles will launch projectiles the same distance?

Bell Work 4/26/131. What is the shape of a projectile?

2. What angle will launch a projectile farthest?

3. What angles will launch projectiles the same distance?

4. List 3 things that affect the range (distance) of a projectile.

Projectiles with Air Resistance

• The optimal angles to send balls flying the farthest distances are around 40°. For example, for kicking or punting a football, you yield the largest distance at a launch angle between 35° and 40°. If you throw a small ball, such as one used in track and field events or a baseball, the ball is much smaller. Thus, the friction plays a smaller role in the movement. Then the best angle is almost 45°.

Projectile Motion

Shoot a Monkey!

• http://www.youtube.com/watch?v=cxvsHNRXLjw

Citing a rifle in

• Can an object be moving upwards if nothing is pushing it?

• Can an object be moving horizontally if nothing is pushing it?

• Is force required to keep an object in motion? (Newton’s ______ Law)

Bell Work

• Which direction do you think the doughnut will travel when the string breaks?

Schedule Monday Check HW (Study guide), Review questions, Egg Drop

Tuesday

Notes on Circular Motion & OrbitsEgg Drop

WednesdayNotes on Orbits & WeightlessnessEgg Drop

ThursdayReview Questions & Finish Egg Drop Project

Friday

Test Egg Drop Project

Today you are going to…take notes on circular motion.

So you can…understand the direction of acceleration & velocity in circular motion and “centrifugal” force.

You’ll know you’ve got it when you can • Accurately answer the circular motion questions.

Circular Motion

Circular Motion

• Objects in circular motion are accelerating towards the center

• Centripetal force – force acting on an object in circular motion; pulls towards center of circle

Circular Motion

• Shape of horizontally thrown projectile

Centripetal Force• Force diagram of object in circular motion

The forbidden F word!

• Centrifugal force – imaginary center fleeing force on an object in circular motion

• NOT REAL

• Caused by inertia…the object wants to keep traveling in a straight line

Car driving in circles

The forbidden F word!

• Circular motion demos

• Why does it stay there? (a law)

• What force acts on it? What direction?

Demos & PuzzlesWhat provides the force • Tom’s puzzle• Penny in balloon• Marble & tape• Ball on string• Color changing ball

• Ball on string through tube with weight

• Question: A ball is being whirled around by a string. If the string suddenly breaks (or is let go), what direction will the ball travel; A, B, C, or D? (Neglect gravity) HAMMER THROW!!!

Doughnut on a string!

• http://www.youtube.com/watch?v=TniQtoapVrQ&feature=related

• Answer: Path ___

• While attached to the string, the ball is forced to follow a curved path. But once the string is gone, no force is exerted and (law of inertia) it follows a straight-line path.

Bell Work 5/1/13Answer questions 1-5 on the back of your

Gravity & Projectile Motion Study Guide.

Today you are going to…take notes on orbits!

So you can…understand how satellites, moons, and planets orbit things.

You’ll know you’ve got it when you can • Accurately answer the questions.

Projectile Motion & Orbits

Projectile Motion & Orbits

• Force diagram of object in circular motion– (this should be earlier in slide show, when

circular motion first mentioned)

Projectile Motion & Orbits

• Objects orbiting Earth are in free fall!– They’re falling!– Gravity acts as the centripetal force– Cannonball!

Satellites!

Earth satellite - projectile moving fast enough to fall continually around Earth rather than into it.

The orbital speed for an object closely orbiting Earth is about 8.0 km/s. That is 29,000 km/h (18,000 mi/h).

Earth Satellites

In the curvature of Earth, the surface drops a vertical distance of nearly 5 meters for every 8000 meters tangent to its surface.

Earth Satellites

For a satellite close to Earth, the time for a complete orbit around Earth, its period, is about 90 minutes.

Earth Satellites

A satellite must stay 150 kilometers (94 miles) or more above Earth’s surface. Why can’t we put a satellite into orbit at low altitudes on Earth?

Earth Satellites

A satellite in circular orbit close to Earth moves tangentially at 8 km/s (5 mi/s). During each second, it falls 5 m.

To escape Earth’s gravity, an projectile must be launched at a velocity of 11.186 km/s = 25,000 mph.

Rockets aren’t projectiles…they don’t need to go this fast. The firing of the rocket provides a constant force.

Pioneer 10, launched from Earth in 1972, escaped from the solar system in 1984 and is wandering in interstellar space.

Escape Velocity

Space Junk!

Bell Work 4/8/11 – 4 minutes1. Convert the following weight to Newtons.

A. 16 lb bowling ball Find the mass of the above in kilograms.

2. Explain how satellites orbit Earth.

Bell Work1. Get your notes & study guide out & finish the

last questions.

Schedule Monday

Gravity Notes & Questions

Tuesday

Circular motion! Build Egg Drop Project

Wednesday

Orbits! Build Egg Drop Project

Thursday

Review Questions & Build Egg Drop Project

Friday

Review & Build Egg Drop Project

Monday

Test!

Tuesday

Test Egg Drop Project

Weightlessness!

Circular Motion & Gravitation 87

Weight & Weightlessness• How would it feel to be weightless?

• How do you feel your weight?

Circular Motion & Gravitation 88

Weight & Weightlessness• What you feel as your “weight” is a

sensation due to the normal force

• Just because you don’t feel your weight, doesn’t mean you’re weightless!

• Astronauts in space are not really weightless.

Circular Motion & Gravitation 89

Weight & Weightlessness• Astronauts are just in constant freefall!

Nothing is holding them up. They feel no normal force, so they feel weighless. They float in the space station because the space station is falling with them.

• Since there’s nothing holding them up, they feel weightless!

• Drop Han Solo!

Circular Motion & Gravitation 90

Weight & Weightlessness

Would you like to be weightless?

Zero-G

• People On Vomit Comet

• http://www.youtube.com/watch?v=N6ZJnIJRUCI&feature=related

• Water balloons in zero gravity http://www.youtube.com/watch?NR=1&feature=fvwp&v=gTqLQO3L4Ko

end

Freefall on planets

What all is the same on the surface of Earth? Figure out that everything else must be equal to acceleration due to gravity.

Egg Drop!• You may purchase more materials during project.

• Materials list (5 pts)– Include quantity, description, price, total price, and net price.– Explain the purpose/advantage of each material– Don’t spend it all. You may purchase more materials during project.

• Blue print (10 pts)– Anyone looking at the blueprint should be able to build it– Everything must be to scale (1in = 1 square)– Explain how things are attached, lengths of string

• Newspaper: • Half Sheet 11.5” x 22.7” Full sheet 22.7” x 22.7”

• Don’t break your egg!– If you do, you will have to clean it up.

• Make sure to calculate average speed & show all work.

• Winners get a free homework pass!

Materials List# Item Cost Total

2 Full sheet of newspaper

6 Straws

7 12” pieces of tape

Net Cost

Egg Drop!• Answer the following questions in complete sentences on

your graph paper.

1. Explain how your design relates to what you know about air resistance and freefall. How is it going to cause the egg to fall slowly?

2. If you had to name a possible problem with your contraption, what would it be? (What might go wrong?)

3. Hopefully your egg stopped accelerating pretty soon after you let it go. What 2 forces were equal at this point?

4. If there were 2 eggs in your basket, would it have fallen faster? Why or why not?

5. Were there any problems with your project? How could you improve upon it (even if there weren’t problems)?

Bell Work 4/11/12

1. What is a satellite?

2. What are the forces acting on a satellite?

3. How long does it take a satellite to orbit Earth?

4. Can we see satellites with the naked eye?

5. How fast do you have to throw a ball to throw it off of the planet?

• Pluto has a mass of 1125 x 1022 kg and an equatorial radius of 1195 km. (a) Calculate the acceleration due to gravity on the surface of Pluto. (b) A python weighs 980 N on Earth. How much would it weigh on Pluto?

MP = 1024 kgrP = 1195 km = 1195000 m = 1.195 x 106 m G = 6.67 x 10-11 N m2/kg2

g = G MP/rP2

g = (6.67 x 10-11)(1024)/(1.195 x 106 )2

g = 4.78 x 10-20 m/s2

WE = 980 NgE = 9.8 m/s2

gP = 0.59 m/s2

WP = ? N

WE = mgE

980 = m(9.8) 100 kg = m

W = mg = (100)(4.78 x 10-18m/s2) = 4.78 x 10-18 N

• The elephant and the feather each have the same force of gravity.• The elephant has more mass, yet both elephant and feather

experience the same force of gravity.• The elephant experiences a greater force of gravity, yet both the

elephant and the feather have the same mass.• On earth, all objects (whether an elephant or a feather) have the

same force of gravity.• The elephant weighs more than the feather, yet they each have the

same mass.• The elephant clearly has more mass than the feather, yet they each

weigh the same.• The elephant clearly has more mass than the feather, yet the

amount of gravity (force) is the same for each.• The elephant has the greatest acceleration, yet the amount of

gravity is the same for each.

Bell Work 4/8/11 – 5 minutes1. Convert the following weights to Newtons.

A. 16 lb bowling ball B. 17 lb cat

C. 20,000 lb truck

2. Find the mass of the above in kilograms.

3. If an object has reached terminal velocity, what is the net force on the object? What’s its acceleration?

4. T/F An object in orbit is actually falling.

Bell Work 4/4/11 – 5 minutes

START NEW MONDAY BELL RINGER FOR 4TH QUARTER

1. Define mass according to chemistry and according to physics.

2. W5SAYW

Bell Work 3/30/12 – 5 min

1. Robbie can throw a 3.0 kg medicine ball with an acceleration of 10.0 m/s2. What acceleration could he give a 9.0 kg medicine ball? Show your work!

2. If you were in a plane, would your weight or mass change? Why?

The moon has a radius of 1.74 million meters and a mass of 7.32x1022 kg. In both MKS and FPS units, determine the acceleration due to gravity on the lunar surface.

M = 7.32 x 1022 kg r = 1,740,000 m = 1.74 x 106 m a = ?

a = GM r2 a = (6.67 x 10-11)(7.32 x 1022 kg ) (1.74 x 106)2

48.824 x 1011

3.02 x 1012

16.17 x 10-1

1.62 m/s2

Bell Work 4/11/11 – 5 minutesMass (kg) Weight on Earth

Newtons Pounds

1. 1 kg ____N ____lbs

2. 50 kg ____N ____lbs

3. 0.102 kg ____N ____lbs

4. _____ kg 500 N ____lbs

5. _____ kg 50 N ____lbs

6. _____ kg ____N 2,000 lbs

7. W5SAYW

Bell Work 3/29/12 – 5 min1. A force of 250.0 lbs acts on an object with a

mass of 8.0 kg. What’s it’s acceleration?

2. What is gravity?

Bell Ringer 4/1/11 – 2 min

1. If the mass of an object magically doubled, the force of gravity between it and other objects __________.

2. If the distance between two objects doubles, the force of gravity between them is ____ what it was.

Bell Work 4/7/11 – 5 minutesUse the conversions between lbs, kg, and N in your notes to answer

the following questions.

1. What is the difference between mass and weight? Give 2 units that measure weight and 1 unit that measures mass.

2. Change the following weights to Newtons. 12 lb bowling ball 117 lb teen 1600 lb car

3. Find the weight of the following masses in Newtons AND pounds.

1 kg 5 kg 1000 kg

If Pandora has a mass of 5.00 x 1024 kg and a radius of

6.00 x 103 km, find the weight of a 110 kg Na’vi on Pandora’s surface. (Pay attention to the units!)

MP = 5.00 x 1024 kg mN = 110 kg r = 6.00 x 103 km = 6.00 x 106 m W = Fg =?

Fg = GMPm r2 Fg = (6.67 x 10-11)(5.00 x 1024 kg )(110 kg)

(6.00 x 106)2

Fg = 1019 N

Tips for using the G equation.

• Make sure you square r!

• You’ll be dealing with big numbers…don’t forget the exponents! “x 10-11”!

• Double check your answers.

Satellite Motion

1. What is a satellite?

2. What are the forces acting on a satellite?

3. How long does it take a satellite to orbit Earth?

4. Can we see them with the naked eye?

5. How fast do you have to travel to get escape this planet?

The speeds of the bowling ball and the satellite are not affected by the force of gravity because there is no horizontal component of gravitational force.

14.2 Circular Orbits

The satellite is always moving at a right angle (perpendicular) to the force of gravity.

• It doesn’t move in the direction of gravity, which would increase its speed.

• It doesn’t move in a direction against gravity, which would decrease its speed.

• No change in speed occurs—only a change in direction.

14.2 Circular Orbits

For a satellite in circular orbit, no force acts along the direction of motion. The speed, and thus the KE, cannot change. What force or forces hold satellites in orbit?

14.4 Energy Conservation and Satellite Motion

A satellite in circular orbit close to Earth moves tangentially at 8 km/s (5 mi/s). During each second, it falls 5 m beneath each successive 8-km tangent.

What happens to the velocity of a satellite as the distance from Earth increases?

14.2 Circular Orbits