Download Practice Clicker Questions: Momentum, Impulse, Work and Energy

Practice Problem Set 3
Momentum
Impulse
Energy
If both the mass and velocity of an object are
doubled, its momentum
1. remains
unchanged.
2. is doubled.
3. is quadrupled.
4. decreases.
0%
1.
0%
2.
0%
3.
0%
4.
Your friend says that impulse equals momentum.
This statement isn’t correct, and the missing word
is
1.
2.
3.
4.
work.
acceleration.
speed or velocity.
change.
0%
1.
0%
2.
0%
3.
0%
4.
A car and a large truck roll down a hill and reach the
bottom at the same speed. Compared with the momentum
of the car, the momentum of the truck is
1.
2.
3.
4.
less.
the same.
more.
none of the
above.
0%
1.
0%
2.
0%
3.
0%
4.
A 1-kg ball moves at 10 m/s and a 10-kg ball
moves at 5m/s. Compared with the 1-kg ball, the
10-kg ball has
1. the same
momentum.
2. 5 times as much
momentum.
3. 10 times as much
momentum.
4. 100 times as much
momentum.
0%
1.
0%
2.
0%
3.
0%
4.
Zombies have invaded the campus, and you only have a
baseball bat to defend yourself. You take a swing at an
attacking zombie. When both the force and time of contact
are doubled, the impulse on the zombie’s head will be:
1.
2.
3.
4.
unchanged.
doubled.
quadrupled.
decreased.
0%
1.
0%
2.
0%
3.
0%
4.
If the speed of a car doubles, what else doubles?
1.
2.
3.
4.
Its momentum.
Its kinetic energy.
Both of the above.
Neither of the
above.
0%
1.
0%
2.
0%
3.
0%
4.
When you catch a fast-moving baseball with your
bare hand, a good idea is to extend the amount of
time it takes to bring the ball to rest. Why?
1.
2.
3.
4.
The impulse of the ball
on your hand is
reduced.
The force of the impact
on your hand is
reduced.
The change in
momentum is reduced.
All of the above.
0%
1.
0%
2.
0%
3.
0%
4.
Whereas impulse involves force and time, work
involves force and
1.
2.
3.
4.
energy.
acceleration.
distance.
power.
0%
1.
0%
2.
0%
3.
0%
4.
Yoda uses the Force to lift Luke Skywalker’s X-wing out of
a swamp. He moves the X-wing 3 meters vertically with a
force of 50,000 N. How much work did Yoda do on the Xwing?
1.
2.
3.
4.
5.
6.
150,000 J
150,000 N
50,000 J
50,000 N
100,000 J
100,000 N
0%
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
6.
How much potential energy was gained by the X-wing
when it was lifted 3 meters? Assume that the mass of the
X-wing is about 5,000 kg and that the gravity on Dagobah
is the same as that on Earth.
1.
2.
3.
4.
5.
5,000 J
100,000 J
50,000 J
15,000 J
150,000 J
0%
1.
0%
0%
2.
3.
0%
0%
4.
5.
A 1-kg iron ball and a 10-kg iron ball are dropped from rest
from the top of a building. Assume that air-resistance is
negligible. Just before hitting the ground below, compared
with the 1-kg ball, the 10-kg ball has
1.
2.
3.
4.
less momentum and KE.
the same momentum
and KE.
10 times as much
momentum and 10
times as much KE.
10 times as much
momentum and 100
times as much KE.
0%
1.
0%
2.
0%
3.
0%
4.
When a car is braked to a stop, unless it is a
hybrid, a majority of its kinetic energy is
transformed to
1. stopping energy.
2. potential energy.
3. mechanical
energy.
4. heat.
0%
1.
0%
2.
0%
3.
0%
4.
A car increases its velocity from 50 km/h to 100
km/h. How much greater will its kinetic energy
become?
1. Twice as much.
2. 4 times more.
3. It remains the
same.
4. 50% more.
0%
1.
0%
2.
0%
3.
0%
4.
• A car with a 70 kg test dummy inside is moving
with a constant velocity of 20 m/s (~50 mph).
The car experiences a head-on collision with a
concrete wall and the test dummy inside is
brought to rest in 0.5 seconds.
Calculate the initial momentum of the test dummy.
Remember that the test dummy is moving at the
same velocity as the car.
1.
2.
3.
4.
5.
70 kg·m/s
20 kg·m/s
1,400 kg·m/s
0 kg·m/s
700 kg·m/s
0%
1.
0%
2.
0%
0%
3.
4.
0%
5.
What is the change in momentum or impulse that
is imparted on the test dummy when it is brought
to rest in the collision?
1.
2.
3.
4.
5.
70 kg·m/s
20 kg·m/s
1,400 kg·m/s
0 kg·m/s
700 kg·m/s
0%
1.
0%
0%
2.
3.
0%
0%
4.
5.
Now that you know the change in momentum
(impulse), calculate the average force that a seat
belt would need to apply to the test dummy in
order to bring it to rest in 0.5s
1.
2.
3.
4.
5.
2,800 N
14,000 N
700 N
1,400 N
70 N
0%
0%
0%
0%
1.
2.
3.
4.
0%
5.
• If 1N is 0.225 lbs, then 2,800 N is 630 lbs being
exerted on the dummy by the seat belt to bring it
to rest in 0.5 s from about 50 mph.
• The duration or amount of time of impact must
be greater in order to reduce the force of impact!
• If time of impact was doubled (1 s), then how
much would the force be?
If the dummy is not held in place by a seatbelt, then it flies
forward on impact. Why does the dummy move forward
even after the car has been brought to rest?
1. A force from the
car seat pushes
the dummy
towards the front
of the car.
2. The test dummy
continues to move
due to its inertia.
0%
1.
0%
2.