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Question 1
An open cart rolls along on frictionless axles
while it is raining. As it rolls, what happens
to the speed of the cart as the rain collects
in it? (Assume that the rain falls vertically
into the cart.)
A) speeds up
B) maintains constant speed
C) slows down
D) stops immediately
Question 2
An 18-wheeler and a Volkswagon Beetle are
rolling along with the same momentum. If
you exert the same force with the brakes to
stop each one, which takes a longer time to
bring to rest?
A) 18-wheeler
B) Volkswagon beetle
C) same for both
D) impossible to say
Question 3
Which is an example of a perfectly elastic
collision?
A) A wet tissue thrown at the wall.
B) The cue ball striking the 8-ball in a
billiards game.
C) A rubber ball bouncing off the floor.
Question 4
An astronaut is taking a space walk when his
tether breaks. He has a big drill. How can he
get back to the space ship?
A) Face away from the
ship and throw the
drill forward
B) Face the ship and
throw the drill forward.
C) Throw the drill towards
the tether.
Question 5
Car A is traveling west with speed 20 m/s when
it collides with Car B, traveling east at 10 m/s.
Which of the following are possible velocities of
the cars after the collision? The cars have the
same mass.
A) Car A 10 m/s west, Car B 20 m/s east
B) Car A 5 east, Car B 25 m/s west
C) Both cars 5 m/s west
D) Car A 18 m/s west, Car B 2 m/s west
Question 6
The square shown below is clearly has its
center of mass at the center. Suppose the
square is cut in two pieces and the pieces
are rearranged as shown. The center of
mass of this object has moved
A) up and to the right.
B) up and to the left.
C) up only.
D) down and to the left.
E) down and to the right.
Question 7
As a kid playing on the playground, you would bend
your knees when you landed after jumping off the
monkey bars to reduce the "sting" in your feet. This
worked because
A) bending your knees gave you upward
momentum which partly canceled the downward
momentum.
B) bending your knees lowered your center of
gravity reducing the force of your fall.
C) bending your knees increased the time of
contact for the ground to bring you to rest.
D) you didn't do it on purpose, your knees just
buckled.
Question 8
As a linebacker on the football team, which
player would be the easiest for you to stop
when you tackle him?
A) The 350-lb lineman who can cover 10
yards in 2.5 seconds.
B) The 160-lb running back, who can make
it down the field in ten seconds.
C) The 240-lb halfback, who can make it
down the field in twenty seconds.
D) They are all equally hard to stop.
Question 9
Two forces produce equal impulses, but the
second force, F2, acts for a time twice that of
the first force, F1. Which force, if either, is
larger?
A) F1
B) they are the same
C) F2
Question 10
A 280-lb linebacker running down the field at
7 m/s tackles a 240-lb halfback running up
the field at 9 m/s. Will the halfback gain or
lose yards after he is tackled?
A) gain
B) lose
C) neither gain nor lose
Question 11
Two objects with different masses have the
same kinetic energy. Which has the larger
magnitude of momentum?
A) the larger mass
B) the smaller mass
C) they have the same momentum
D) impossible to tell
Question 12
Maggie drops a stuffed bear over the side of
her crib. It hits the floor with speed v and
comes to rest. She then drops a rubber ball
with the same mass from the same height,
and it bounces back upwards with speed v.
Compare the change in momentum of the
bear and the ball.
A) Dpbear = Dpball
B) Dpbear = 2Dpball
C) Dpbear = ½Dpball
D) Dpbear = -Dpball
Question 13
You peddle frantically to get your bicycle up to
a speed of 15 m/s. On level ground, you
relax and start to coast. Your speed
A) stays the same, because momentum is
conserved.
B) increases, now that you are not
expending energy turning the pedals.
C) decreases, as there are still forces acting
on the bicycle.
Question 14
An urban legend has it that the RAF was
testing the windshields of their aircraft for
bird strikes using a chicken cannon given to
them by the USAF. The windshields kept
breaking because they were using frozen
chickens instead of fresh ones. Using your
knowledge of physics, you would reason
that the legend is
A) false - frozen and thawed chickens have
the same momentum on impact.
B) true - frozen chickens are harder and
come to rest in a shorter time,
increasing the force.
Question 15
You paddle your own canoe forward by
pushing back on the water. If you can
change the velocity of 7.3 kg of water by
3.0 m/s with each stroke, your speed
changes by (myou + mcanoe = 93 kg)
A) 226 m/s
B) 38 m/s
C) 4.2 m/s
D) 0.24 m/s
Question 16
You are knocking out sheetrock with a sledge
hammer. Which is more efficient, for you to
swing the hammer so it stops at the surface
of the sheetrock, or to swing the hammer so
that it goes past the surface of the sheetrock
before stopping?
A) At the sheetrock, because the most
energy is dissipated there.
B) Past the sheetrock, so the hammer is in
contact with the sheetrock for a
longer time.
Question 17
A boxcar with mass m moving to the right with
speed v collides with a second boxcar of the
same mass which is at rest. After the
collision, both boxcars move off to the right
with speed v/2. In this collision
A) momentum is conserved.
B) energy is conserved.
C) momentum and energy are conserved.
D) neither momentum nor energy is
conserved.
Question 18
Red Rover, Red Rover, let Leslie come over. In
this childhood game, you try to stop and catch
a person who is running directly at you. Who
would you rather pick?
A) Sean, who weighs 450 N and can run
5.4 m/s.
B) Meihong, who weighs 270 N and can run
8.8 m/s.
C) Deidra, who weighs 340 N and can run
7.2 m/s.
Question 19
Suppose you throw a rubber ball at an
approaching truck. When it bounces back to
you, is it traveling faster, slower, or with the
same speed at which you threw it?
A) faster
B) slower
C) at the same speed
Question 20
When you lift a heavy suitcase in one hand,
you lean
A) toward the suitcase, to move your center
of gravity under the suitcase.
B) away from the suitcase, to shift your
center of gravity towards your feet.
C) towards the suitcase, since it is weighing
you down.
Answer Key – Chapter 7
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