chapter 5

Chapter 5Matter in Motion

Motion

When an object changes distance over time.

How do you know if an object is in motion?

Reference point Is an object that motion is measured against What is the reference point in this picture.

Frame of Reference Video 1960

Speed Formula ex. 66m/s

AS=Average Speed

TD=Total Distance

TT=Total Time

Average Speed VS Actual Speed

0

1

2

3

4

5

6

7

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Time (min)

Dis

tan

ce

(k

m)

Series2

Series3

Average Speed

Actual Speed

Solve for AS, TT, or TD

If you walk for 1.5 hours and travel 7.5 km what is your average speed?

AS = TD TT

AS = 7.5 km 1.5 hr

AS = 5 km/hr

Solve for AS, TT, or TD

If you ride a bike .5 hours and cover 4,000 m what is your average speed?

AS = TD TT

AS = 4,000 m .5 hr

AS = 8,000 m/hr

Solve for AS, TT, or TD

If the average speed of a car is 110 km/hr how long will it take that car to travel 715 km?

TT = TD AS

TT = 715 km 110 km/hr

TT = 6.5 hr

Solve for AS, TT, or TD

If the average speed of a tricycle is 5 km/hr what distance will it cover in 10 hours?

TD = AS * TT TD = 5 km/hour * 10 hours TD = 50 km

Velocity Formula ex. 66m/s West

V= Velocity

TD=Total

Distance

TT=Total

Time

+ direction

Velocity- Speed in a given direction w

es

t (m

)

Combining Velocity

When you combine two velocities that are in the same direction, add them together to find the resultant velocity.

Combining Velocity

When you combine two velocities that are in opposite directions, subtract the smaller velocity from the larger velocity to find the resultant velocity. The resultant velocity is in the direction of the larger velocity.

Combining Velocity

What happens when the person and the bus go in the same direction?

___________________________________

___________________________________ What happens when the person and the bus are

going in different directions?

___________________________________

___________________________________

Look at p. 110 and complete the self check. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

How do we measure a change in velocity? What is a change in velocity called?

Acceleration- The rate at which velocity is changing. Term “Acceleration” is used when velocity

increases.Term “Deceleration” is used when velocity

decreases.A “change in direction” but not speed is

also acceleration.

Acceleration Formula

∆ = change

Acceleration = ∆V ∆V= Final V- Starting V t

Acc.= Final V - Starting V t

Units for Acceleration

* Sample Problem: What is the acceleration if we speed up from 10 Km/h to 30 km/hr in 10 seconds?

Acceleration = ∆V = 30 km/hr - 10km/hr

t 10 sec

Acceleration = 2 km/hr/s

1. A plane passes over point A with a velocity of 8000 m/s north. Forty seconds later it passes over point B with a velocity of 10,000 m/s north. What is the planes acceleration from A to B?

Acceleration = ∆V 10,000 m/s – 8,000 m/s

t 40 s

Acc= 50 m/s/s or m/s2

2. A coconut falls from the top of a tree and reaches a velocity of 19.6 m/s when it hits the ground. It takes two seconds for the coconut to hit the ground. What is its acceleration?

Acceleration = ∆V 19.6 m/s – 0 m/s

t 2 s

Acc= 9.8 m/s/s or m/s2

1. No Acceleration Graph

00.5

11.5

22.5

33.5

44.5

0 1 2 3 4

Time (s)

Vel

oci

ty (

m/s

No

rth

)

2. Negative Acceleration Graph

02468

1012141618

0 1 2 3 4

Time (s)

Vel

oci

ty (

m/s

No

rth

)

3. Constant Positive Acceleration Graph

0123456789

0 1 2 3 4

Time (s)

Vel

oci

ty (

m/s

No

rth

)

4. Positive Acceleration

0

2

4

6

8

10

12

14

0 1 2 3 4

Time (s)

Vel

oci

ty (

m/s

No

rth

)

1

2

3

1

2

3

4

5

1

2

3

4

5

1

2

3 4

5

Time (s) Time (s)

Vel

oci

ty (

m/s

)

Po

siti

on

(m

)

Time (s) Time (s)

Vel

oci

ty (

m/s

)

Po

siti

on

(m

)

C

1.

______14km

4.

______ 6 hr

7.

______ 14mi

10.

______1.4 m

2.

_____30 m/s

5.

____12cm/s2

8.

______3.2 s

11.

______6

cm/min/sec

3.

_____34 min

6.

____150mph

9.

______25ft

12.

______3

Km/hr/sec

D T D D

S A T A

T S D A

13. Goldie Goldfish, a speed swimmer, loves to race around the park’s pond, which is 0.5 miles around. If she can swim 20 laps around the track in 2 hours, what is her average speed?

What is missing?

20 * 0.5 = 10 mi

AS= TD/TT

10mi / 2 hr

AS= 5 mph

14. It takes Stu, a slimy slug, 20 minutes to travel from his favorite bush to the local trash can (a trip of 30m), how far can he travel in 1 hour (60 min)?

What is the first step.

AS= TD/TT

30 m / 20 min

AS= 1.5 m / min

Now what?

S * T = D

1.5 m / min * 60 min = 90m

15. At exactly 2:00 pm, Speedy the Snail crawls onto a meter stick at the 10 cm mark. If he reaches the 65 cm mark at exactly 2:10 pm, what is his speed?

What is the first step.

65cm -10cm= 55cm (which is the total distance)

Now what?

AS= TD/TT

AS= 55cm /10 min

AS= 5.5 cm / min

16. If it takes Leaping Louie 5 minutes to jump 3 blocks, how long will it take for him to jump 15 blocks?

What is the first step.

3 blocks / 5 min = .6 blocks / min

Now what?

15 / .6 block / min = 25 min

16. If Bert the Bat travels eastward at 40 mph with a tail wind of 6 mph, what is his actual speed?

Don’t use a formula just think about it!

Add the bat’s velocity to the wind’s 46 mph

6mph east 40 mph east

18. Toon Train is traveling at the speed of 10 m/s at the top of a hill. Five seconds later it reaches the bottom if the hill and is moving at 30 m/s. What is the rate of acceleration of Toon Train?

Acceleration = ∆V

t

30m/s – 10 m/s =

5 s

Acc= 4 m/s/s down

19. Pete the Penguin loves to sled down his favorite hill. If he hits a speed of 50 m/s after 5 seconds, what is his rate of acceleration? Hint: He starts at 0 m/s at the top of the hill.

Acceleration = ∆V

t

50m/s – 0 m/s =

5 s

Acc= 10 m/s/s down

20. Monster Mike’s truck decelerates from 72 m/s to 0 m/s in 6 seconds. What is his rate of deceleration?

Acceleration = ∆V

t

0m/s – 72 m/s =

6 s

Acc= -12 m/s/s forward

Quick Review

What does A show for distance/time? What does B show for distance/time? What does C show for distance/time?

Time (min)

Dis

tan

ce (

km)

Quick Review

What does A show for velocity /time? What does B show for velocity /time? What does C show for velocity /time?

Time (min)

Ve

loci

ty (

km/ m

in e

ast

)

Speed and Acceleration Part 1:

Does the speedometer of a car read average speed or instantaneous speed?

______________________________ How do you know?

Instantaneous

It shows the speed you are going right now, not the speed you were going or are going to go. It also changes as you push the gas.

Speed and Acceleration Part 1:

If the speedometer of your car reads a constant speed of 40km/hr, can you say the car has a constant velocity? ______

Explain your answer.

No

You can’t say this because the car could be changing direction. Ex. Nascar

a) Which two controls on a car cause a change in speed?

_________________________

_________________________

b) Which additional control causes a change in velocity?

_________________________

Gas Pedal

Brake

Steering Wheel

What is the acceleration of a car that travels in a straight line at a constant speed?

_________________________________

Describe a situation in which you can accelerate even though your speed doesn’t change.

___________________________________

The acceleration of the car would be 0 m/s/s

Pac-man.

Part 2: Calculations

Formula: Work:

Answer:

6. It takes Serina 0.25 hours to drive to school. Her route is 16 km long. What is Serina’s average speed on her drive to school?

S= D/TS= 16 km

.25 hr

S= 64 km/hr

Part 2: Calculations

Formula: Work:

Answer:

7. In a competition, an athlete threw a flying disk 139 meters through the air. While in flight, the disk traveled at an average speed of 13.0 m/s. How long did the disk remain in the air?

T=D/VT= 139m

13 m/s

T= 10.69 s

Part 2: Calculations

Formula: Work:

Answer:

8. A runner covers the last straight stretch of a race in 4 s. During that time, he speeds up from 5 m/s to 9 m/s. What is the runner’s acceleration in this part of the race?

Acc= Vf –Vs TT

Acc= 9m/s – 5 m/s 4 s

Acc.= 1 m / s / s

Part 2: Calculations

Formula: Work:

Answer:

9. If you shout into the Grand Canyon, your voice travels at the speed of sound (340 m/s) to the bottom of the canyon and back, and you hear an echo. How deep is the Grand Canyon at a spot where you can hear your echo 5.2 seconds after you shout?

D=T * VD= 5.2 * 340

D= 1768 m

Part 2: Calculations

Formula: Work:

Answer:

10. Falling objects drop with an average acceleration of 9.8 m/s2. If an object falls from a tall building, how long will it take before it reaches a speed of 49 m/s?

T = Vf- Vs

Acc

T= 49 – 0 9.8

T= 5 s

Part 2: Calculations

Formula: Work:

Answer:

11. Josh rolled a bowling ball down a lane in 2.5 s. The ball traveled at a constant acceleration of 1.8 m/s2 down the lane and was traveling at a speed of 7.6 m/s by the time it reached the pins at the end of the lane. How fast was the ball going when it left Tim’s hand?

Vs = Vf –(A * T)Vs = 7.6 m/s – (1.8 * 2.5)

Vs = 3.1 m/s

Acceleration Practice: Part 1: True or False

1. _______ If you slow down on your bike you accelerate?

Why?___________________________________

2. _______ If you ride your bike at a constant speed, you cannot accelerate?

Why?__________________________________

3. _______Changing the speed and changing the direction of your bike are both examples of acceleration?

Why?___________________________________

True

False

True

Acceleration Practice: Part 2: Acceleration?

4. You are riding your bike at

Force 5-2 p. 115 - 118

Force is a push or a pull Forces have the ability to change an

objects motionStartingStoppingSpeeding upSlowing downChanging direction

Forces may change an objects shape Forces give energy to an object All of the forces acting on an object

together are known as net forces Balanced Forces: are equal net forces

No movement or change in movement occurs

Unbalances Forces: are unequal forces Some change in movement occurs

Where are the unbalanced forces?

Left

What is the motion of this object?

Are the forces balanced?

Forces can be represented with arrows called vectors. Vectors show the direction and magnitude of

a force. Forces are measured in Newtons (N).

Larger Force Smaller Force

MAGNITUDE

Chapter 5 Section 3 Friction is a force that opposes motion

between surfaces that are touching. Even surfaces that appear smooth have

rough edges.

On p. 119

Two ways to Increase friction.

1. Make the surface rougher.

2. Greater force.

Two ways to Decrease friction.

1. Make the surface smoother.

2. Less force.

Be Careful!

Friction is not increased by increasing surface area if the mass stays constant.

Types of friction

Sliding Rolling Fluid Static

Examples of types of Friction

Sliding

_____________________

_____________________

_____________________

Examples of types of Friction

Rolling

_____________________

_____________________

_____________________

Examples of types of Friction

Fluid- Remember this is a liquid or a gas!

_____________________

_____________________

_____________________

Examples of types of Friction

Static- friction with no movement but a force is applied.

_____________________

_____________________

_____________________

Explain this diagram.

5-4 Gravity

Section 5-4Section 5-4

5-4 Gravity Gravity: force of

attraction between objects due to their masses.

Why are astronauts so “bouncy on the moon?

Gravity acts “down”. Earth gravity pulls objects towards the center of the Earth. So no matter where you are on Earth all objects fall “down” to the ground.

What do the apple and the moon have in common? The law of universal gravitation. Describes the relationship between force, mass and

distance. States that all objects in the universe attract each

other through gravitational force. The size of that force depends on the mass of the objects and the distance between the objects.

Small mass, Small distance= Medium Gravity

Large mass, Small distance= Large Gravity

Large mass, Large distance= Small Gravity

If all objects have gravity why don’t you feel it? Earth is so big and close that all other

things are very small or very far making there gravity VERY small.

The two factors that effect gravity are: 1. Distance 2. Mass

Weight V.S. Mass

What does this diagram show?

Weight V.S. Mass

Our mass is in Kilograms but our weight is in Newtons…. Why?

Weight is the force of gravity. Forces are measured in Newtons (N) so Weight is measured in Newtons (N).

Weight V.S. Mass on Earth Using the data below, explain the relationship between

weight and mass on earth? What is the gravity on Earth? What is gravity on the Moon?

EarthEarth MoonMoonMass Weight Mass Weight

60 Kg 588 N 60 Kg 100 N

80 kg 784 N 80 kg 133 N

100kg 980 N 100kg 166 N

What is the formula for weight?

WEIGHT (N)

MASS(Kg)

AccelerationDUE TO

GRAVITY(on earth 9.8 m/s/s)

Weight Mass

Balance Measure of gravity Constant on earth Measured in (N) Changes with gravity 6 X less on the moon

Spring Scale Amount of matter Constant on earth Measured in (g) Never changes Remains the same

when gravity changes

Directed Reading 5-21. All forces have size and direction True / False

2. A force is a push or a pull. True / False

3. Forces are expressed in liters. True / False

4. You can exert a push without there being an object to receive the push. True / False

5. Name three things that you exert a force on while doing your home work?

Newtons (N)

6. In which of the following situations is a force being exerted?

A. A woman pushes the elevator button.

B. a pile of soil sits on the ground

C. Socks cling together when they come out of the dryer.

D. Magnets stick to the refrigerator.

7. In figure 8 on p. 116 how does the net force help the students move the piano?

______________________________Since the forces are in the same direction you add the forces together.

Directed Reading 5-28. Suppose the dog on the left in figure 9, on

page 117, increased its force to 13 N. Which dog would win the tug-of-war? Explain?

______________________________________________________________________9. Why is it useful to know the net force?

___________________________________10. Forces are unbalances when the net forces

are not = to ______________

The dog on the left will win by 1 N because forces are not negative but positive in a direction.

It can tell you about the motion of an object.

Zero

Directed Reading 5-211. To start or change the motion of an object

you need a (n) __________ force.

12. Forces are balanced when the net force applied to an object is ___________ zero.

13. Are the forces in Figure 10 balanced? ____ How do you know?

_____________________________________

unbalanced

equal to

yes

The cards are not moving or falling.

Directed Reading 5-31. What force is responsible for the painful

difference between sliding on grass and sliding on pavement?

______________________

2. Friction occurs when the hills and valleys of two surfaces stick together.

True / False

3. Why does pavement create more friction than grass?

___________________________________

Sliding Friction

The pavement is rougher than the grass.

Directed Reading 5-34. Why is more force needed to slide the

larger book in Figure 12 on p. 120?

___________________________________

___________________________________

5. Friction is affected by the amount of the surface that is touching.

True / False

The mass is larger so the downward force That is created is larger.

Directed Reading 5-3

6. Hockey puck on ice

7. Crate on loading ramp

8. Wheeled cart pushed

9. air passing a car

A. Sliding Friction

B. Rolling Friction

C. Fluid Friction

D. Static Friction

Directed Reading 5-310. Static friction is at work if you try to drag

a heavy suitcase along the floor and the suitcase (moves or does not move)

11. As soon as an object starts moving, static friction (increases or disappears).

If the suitcase had moved, what type of friction would have been at work?

12. How does friction harm the engine of a car?

___________________________________

___________________________________

13. Why do you need friction to walk?

___________________________________

___________________________________

14. Which of the following will reduce friction?

A. Use a lubricant. B. Make surface smoother.

C. Push surfaces D. Change sliding friction

together. to rolling friction.

It wears down the parts inside the car because of sliding friction.

If there was no friction you would not be able to grip the floor with your shoes.

Section Review p. 1241. Explain why friction occurs?

2. Name two ways friction can be increased?

3. Give an example of Sliding Friction, Rolling Friction, Fluid Friction, Static Friction.

4. How is friction harmful and helpful when you ride a bike?

Directed Reading 5-41. Why did the astronaut in Figure 18 bounce

on the moon?

2. The force of attraction between two objects due to their masses is the force of ______________.

3. Does all matter experience gravity? Explain.

______________________________________

______________________________________

4. The force that pulls you towards your pencil is called ________________ force.

Gravity

Yes because all matter has mass and gravity is a force that an object has b/c it has mass

Gravitational

Directed Reading 5-45. Do scientists think that seeds can sense

gravity? True / False

6. Since all objects are attracted to each other because of gravity, why can’t you see objects moving towards each other? ____________

_____________________________________

_____________________________________

7. How are objects effected by the mass of the earth? ____________________________

b/c the gravity

Of earth is to large for the force of gravity to overcome the force of friction.

Directed Reading 5-4

8. What did Newton find out about the moon and the falling apple? ________________

___________________________________

9. Newton’s law of universal gravitation describes the relationship between all the following except _____.

10. Which of the following are subject to the law of universal gravitation? __________

Both the apple and The moon are being acted upon by gravity.

heat

A, B, C, D

Directed Reading 5-411. If the distance between objects are the

same the gravitational force between two feathers is greater than the gravitational force between two boiling balls. ________

12. If two objects are moved_____________ each other, the gravitational force between them increases.

13. Why is the cat easier to pick up than the elephant?

___________________________________

False toward

Cat has less mass and thus less gravitational force

Directed Reading 5-414. In a _____________ gravity is so great

that even light can’t escape.

15. Why doesn’t the sun’s gravity pull you off earth? ____________________________

16. The gravitational force exerted by an object depends on the _________ of the object. The measure of Earths gravitational force on an object is the objects ________________.

Black Hole

It is very far away.

mass

weight

___

___

___

___

___

___

18. different on the moon

19. Expresses in (N)

20. Expressed in (G)

21. Measure of the gravitational force

22. Value does not change

23. amount of matter in an object

W

W

M

W

M

M24. On Earth mass & weight are constant, which means that they are the same thing. True / False

Section Review p. 129

1. How does the mass of an object relate to the gravitational force the object exerts on other objects?

2. How does the distance between objects affect the gravity between them?

3. Explain why your weight would change as you orbit in a space shuttle but your mass would not.