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Momentum Impulse CollisionsConservationof Momentum

Physics IsPhun!

2

How do you calculate the momentum of an object?

3

How do you calculate the momentum of an object?

Momentum = Mass x Velocity

4

True or False: Momentum is a vector quantity.

5

True or False: Momentum is a vector quantity.

True

6

What is the momentum of a 0.520-kg object moving at a velocity of 14 m/s?

7

What is the momentum of a 0.520-kg object moving at a velocity of 14 m/s?

Momentum = Mass x Velocity

p = mv = (0.520 kg)(14 m/s)

p = 7.28 kg m/sec

8

Of the object’s listed, select the one with the greatest momentum.

A) a .22-caliber bullet fired from a rifleB) a bus speeding along a highwayC) a sprinter running the 100-yard dashD) the Earth in its orbitE) not enough info to answer

9

Of the object’s listed, select the one with the greatest momentum.

A) a .22-caliber bullet fired from a rifleB) a bus speeding along a highwayC) a sprinter running the 100-yard dashD) the Earth in its orbitE) not enough info to answer

10

What is the total momentum of the following situation? Assume there is no friction.

2 kg

1.5 m/s 0.8 m/s

3 kg

11

What is the total momentum of the following situation? Assume there is no friction.

2 kg

1.5 m/s 0.8 m/s

3 kg

Momentum of LH-cart = (2 kg)(1.5 m/s) = + 3 kg m/secMomentum of RH-cart = (3 kg)(- 0.8 m/s) = - 2.4 kg m/sec

Total Momentum = + 3 kg m/sec – 2.4 kg m/sec

= 0.6 kg m/sec

12

An impulse is equal to which of the following?

A) force times distanceB) force of impactC) change in kinetic energyD) change in momentumE) none of these

13

An impulse is equal to which of the following?

A) force times distanceB) force of impactC) change in kinetic energyD) change in momentumE) none of these

14

If a boxer wishes to reduce the force of impact from an

incoming punch, what should they do to the time of impact?

15

If a boxer wishes to reduce the force of impact from an

incoming punch, what should they do to the time of impact?

Increase the time of impact

16

What is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18

seconds?

17

What is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18

seconds?

Change in momentum = impulse = F t

F t = (75 N)(0.18 sec)

F t = 13.5 N sec

18

A Mack truck and bug are traveling towards one another when they collide head-on. Which one experiences the

greater impulse?

A) the Mack truckB) the bugC) they both experience the same impulseD) not enough info

19

A Mack truck and bug are traveling towards one another when they collide head-on. Which one experiences the

greater impulse?

A) the Mack truckB) the bugC) they both experience the same impulseD) not enough info

20

A 1,000 kg rocket is launched from rest to a speed of 2500 m/sec in a time of 2.5

minutes. What was the average force (in Newtons) exerted on the rocket?

21

Change in momentum = Impulse

m v = F t ==> F = m v / t

F = (1000 kg)(2500 m/sec)/(150 sec)

F = 16,667 Newtons

A 1,000 kg rocket is launched from rest to a speed of 2500 m/sec in a time of 2.5

minutes. What was the average force (in Newtons) exerted on the rocket?

22

True or False: Momentum is conserved in all kinds of collisions.

23

True

True or False: Momentum is conserved in all kinds of collisions.

24

Which kind of collision conserves both momentum and kinetic energy?

A) elasticB) inelasticC) bothD) neither

25

Which kind of collision conserves both momentum and kinetic energy?

A) elasticB) inelasticC) bothD) neither

26

Why is it safer to stop an out-of-control car by running into a pond

versus hitting a concrete wall?

27

Why is it safer to stop an out-of-control car by running into a pond

versus hitting a concrete wall?

By running into the pond, the time it takes the car to slow down to a stop

is lengthened. Therefore the stopping force is decreased.

28

Why is it that a bouncing collision is more damaging than a sticking

collision (assuming the same time of impact in each case)?

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A bouncing collision is more damagingbecause the change in velocity, and

therefore the change in momentum, isgreater. This leads to a larger force.

Why is it that a bouncing collision is more damaging than a sticking

collision (assuming the same time of impact in each case)?

30

A 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is 0.078 sec, what was

the force of impact?

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Impulse = Change in Momentum

F t = m v ==> F = m v / t

F = (0.25 kg)(45 m/sec)/(0.078 sec)

F = 144.2 Newtons

A 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is 0.078 sec, what was

the force of impact?

32

When an asteroid collides with the Moon, the Moon drastically changes the

momentum of the asteroid. By how much does the Moon change its

momentum?

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Precisely the same amount

When an asteroid collides with the Moon, the Moon drastically changes the

momentum of the asteroid. By how much does the Moon change its

momentum?

34

A firecracker is sitting on the ground when it is lit. After the explosion, what

is the total momentum of the pieces flying away?

35

A firecracker is sitting on the ground when it is lit. After the explosion, what

is the total momentum of the pieces flying away?

Zero, because the momentum of the firecracker before the explosion was zero,

and momentum must be conserved.

36

A bullet is fired from a heavy rifle. Two questions:

Which one experiences a greater change in momentum?

Which one experiences a greater change in velocity?

37

A bullet is fired from a heavy rifle. Two questions:

Which one experiences a greater change in momentum?Neither, it’s the same

Which one experiences a greater change in velocity?

The bullet.

38

Two billiard balls collide elastically on a table as shown below. Which

picture best represents the motion of ball #2 after the collision?

Bonk!

#1 #1

#2

A

B

C

39

Two billiard balls collide elastically on a table as shown below. Which

picture best represents the motion of ball #2 after the collision?

Bonk!

#1 #1

#2

A

B

C

40

Two carts collide and stick together as shown below. What is the velocity of the carts after they’ve collided? Assume there is no friction.

3 kg

2.5 m/s 1.8 m/s

2 kg

41

Two carts collide and stick together as shown below. What is the velocity of the carts after they’ve collided? Assume there is no friction.

3 kg

2.5 m/s 1.8 m/s

2 kg

Momentum of LH-cart = (3 kg)(2.5 m/s) = +7.5 kg m/sMomentum of RH-cart = (2 kg)(-1.8 m/s) = -3.6 kg m/s

Total Momentum = +3.9 kg m/s

After collision ==> 3.9 kg m/s = (5 kg)v

v = (3.9 kg m/s)/(5 kg) = +0.78 m/sec

42

How many triangles are there in the following figure?

43

35

44

Name the actor and movie that produced this famous quote:

“Boards don’t hit back.”

45

Bruce Lee, inEnter the Dragon

46

In March of 2005, the international space-advocacy organization The Planetary

Society launched what spacecraft?

47

Cosmos 1, the first solar-sail

48

What California gold-rush entrepreneur used his

knowledge of bouncing collisions to design a nearly 90% efficient water wheel?

49

Lester A. Pelton, inventor of the Pelton water wheel

50

Who are a “couple of eccentric guys who have learned how to

do a few cool things”?

Hint: They’ve had an awesome show on the Showtime cable network!

51

Penn & Teller