Q1) The x and y coordinates of the center of mass of the
three-particle system shown below are:
1) 0; 0
2) 1.3m, 1.7m
3) 1.4m, 1.9m
4) 1.9m, 2.5m
5) 1.4m, 2.5m
Q2) Four masses are laid out in a square
pattern as shown. The origin of the x-y
axes is at the center of the lower left
mass. Three of the masses are "m", the
one in the lower left is "2m"
m
m
2m
m
a
What is the x-coordinate of the center of mass?
1) a
2) (1/2)a
5) none of the above
3) (1/5)a
4) (2/5)a
Q3) You are sitting at the left end of a canoe in the middle of a lake. You
carefully begin to walk towards the right end of the canoe. As viewed
from the edge of the lake, as you walk, the CM of the person-canoe
system... (Neglect friction between water and canoe)
1) moves to the right
2) moves to the left
3) stays in the same spot
4) It depends on how fast you move.
Q4) The center of mass of a system of particles remains at the
same place if:
1) it is initially at rest and the external forces sum to zero
2) it is initially at rest and the internal forces sum to zero
3) the sum of the external forces is less than the maximum force of
static friction
4) no friction acts internally
5) none of the above
Q5) Two objects have the same momentum. Do the
velocities of these objects necessarily have (a) the same
directions and (b) the same magnitudes?
1) (a) yes
2) (a) yes
3) (a) no
4) (a) no
(b) yes
(b) no
(b) yes
(b) no
Q6) Two objects with different masses have the same kinetic
energy. Which has the larger magnitude of momentum?
1) the larger mass
2) the smaller mass
3) they have the same momentum
4) impossible to tell
Q7) Padded dashboards in cars are safer in an accident than
nonpadded ones because an occupant hitting the dash has
1) increased time of impact.
2) decreased time of impact.
3) decreased impulse.
4) increased momentum.
Q8) A paratrooper whose chute fails to open lands in the snow; he is hurt
slightly. Had he landed on bare ground, the stopping time would have
been 10 times shorter and the collision lethal. Does the presence of the
snow increase, decrease, or leave unchanged (a) the impulse stopping the
paratrooper and (b) the force on the paratrooper?
1) (a) decrease
2) (a) increase
3) (a) leave unchanged
4) (a) leave unchanged
5) (a) leave unchanged
(b) decrease
(b) decrease
(b) leave unchanged
(b) decrease
(b) increase
Q9) A person attempts to knock down a large wooden bowling pin
by throwing a ball at it. The person has two balls of equal size and
mass, one made of rubber and the other of putty. The rubber ball
bounces back, while the ball of putty sticks to the pin. Which ball
is most likely to topple the bowling pin?
1) The rubber ball
2) The ball of putty
3) It makes no difference
4) Need more information
Q10) A ball bounces off
the floor as shown. The direction of the

impulse of the ball, p , is ...
1) straight up 
2) straight down 
3) to the right 
4) to the left 
Q11) Two cars, one twice as heavy as the other, are at rest on a
horizontal track. A person pushes each car for 5 s. Ignoring friction
and assuming equal force exerted on both cars, the momentum of
the light car after the push is
1) smaller than
2) equal to
3) larger than
the momentum of the heavy car.
Q12) Consider two carts, of masses m and 2m, at rest on an air
track. If you push first one cart for 3 s, and then the other for the
same length of time, exerting equal force on each, the momentum
of the light cart is..
1) four times
4) one-half
2) twice
5) one-quarter
the momentum of the heavy cart.
3) equal to
Q13) Suppose a ping-pong ball and a bowling ball are rolling
toward you. Both have the same momentum, and you exert the
same force to stop each. How do the time intervals to stop them
compare?
1) It takes less time to stop the ping-pong ball.
2) Both take the same time.
3) It takes more time to stop the ping-pong ball.
Q14) Two cars, one twice as heavy as the other, are at rest on a
horizontal track. A person pushes each car for 5 s. Ignoring friction
and assuming equal force exerted on both cars, the kinetic energy
of the light car after the push is
1) smaller than
2) equal to
3) larger than
the kinetic energy of the heavy car.
Q15) (a) Can a single object have kinetic energy but no
momentum? (b) Can a system of two objects have
nonzero total kinetic energy but zero total momentum?
1) (a) yes
2) (a) yes
3) (a) no
4) (a) no
(b) yes
(b) no
(b) yes
(b) no
Q16) If the total momentum of a system is changing:
1) particles of the system must be exerting forces on each other
2) the system must be under the influence of gravity
3) the center of mass must have constant velocity
4) a net external force must be acting on the system
5) none of the above
Q17) An explosion splits an object initially at rest into two pieces
of unequal mass. Which piece has greater kinetic energy?
1) The more massive piece.
2) The less massive piece.
3) They both have the same kinetic energy.
4) There is not enough information to tell.
Q18) A firework shell is launched at 45 degrees, and just as it
reaches the top, with speed V it explodes into two pieces of equal
mass. One fragment is observed to fall vertically down from the
point of explosion. What does the other piece do?
1) Also falls vertically down
2) Recoils backwards from the explosion
3) Continues forward with the same speed (V) it had just before.
4) Continues forward with twice the speed (2V)
5) There can't possibly be enough information to decide.
Q19) Suppose the entire population of Earth gathers in one
location and, at a pre-arranged signal, everyone jumps up. About a
second later, 6 billion people land back on the ground. After the
people have landed, the Earth’s momentum is…
1) the same as before the people jumped.
2) different than it was before the people jumped.
3) impossible to know whether it changed.
Q20) Complete the following statement: Momentum will be
conserved in a two-body collision only if
1) both bodies come to rest.
2) the collision is perfectly elastic.
3) the kinetic energy of the system is conserved.
4) the net external force acting on the two-body system is zero.
5) the internal forces of the two body system cancel in actionreaction pairs.
Q21) Whenever an object strikes a stationary object of equal mass:
1) the two objects cannot stick together
2) the collision must be elastic
3) the first object must stop
4) momentum is not necessarily conserved
5) none of the above
Q22) Blocks A and B have linear momentum with directions
as shown and with magnitudes of 9 kg m/s and
4 kg m/s, respectively. If block A ends up moving to the left,
is the magnitude of its momentum greater than, less than, or
the same as that of block B?
1) greater than
2) less than
3) the same as
Q23) In the four situations indicated in the figure, an object
explodes into two equal-mass fragments. The velocity
vectors of the fragments are indicated. In which situation(s)
was the object stationary before the explosion?
1) a
2) b
3) d
4) b and d
5) a, b, and d
Q24) A small glider is gliding along an air track at some initial speed, hits
a much larger glider, and is observed to bounce back with a final speed
nearly equal to its initial speed.
The magnitude of the momentum of the large glider after the collision is…
1) less than the initial momentum magnitude of the small glider.
2) larger than the initial momentum magnitude of the small glider.
3) necessarily zero.
Q25) A compact car and a large truck collide head on and stick
together. Which undergoes the larger momentum change?
1) car
2) truck
3) The momentum change is the same for both vehicles.
4) Can’t tell without knowing the initial velocities.
Q26) Is it possible for a stationary object that is struck by a moving
object to have a larger final momentum than the initial momentum
of the incoming object?
1) Yes
2) No
Q27) If all three collisions in the figure shown here are totally
inelastic, which bring(s) the car on the left to a halt?
1) I
4) II,III only
2) II
5) All three.
3) III
Q28) Suppose you are on a cart, initially at rest on a track with
very little friction. You throw balls at a partition that is rigidly
mounted on the cart. If the balls bounce straight back as shown in
the figure, is the cart put in motion?
1) Yes, it moves to the right.
2) Yes, it moves to the left.
3) No, it remains in place.
Q29) Two masses m1 and m2 approach each other on a frictionless
table and collide. Is it possible that, as a result of the collision, all
of the kinetic energy of both masses is converted to heat. (If so,
under what circumstances?)
1) Yes
2) No
Q30) A 50.0-kg boy runs at a speed
of 10.0 m/s and jumps onto a cart as
shown in the figure. The cart is
initially at rest.
If the speed of the cart with the boy on it is 2.50 m/s, what is the mass of
the cart?
1) 150 kg
4) 175 kg
2) 210 kg
5) 260 kg
3) 300 kg
Q31) A cart of mass m is moving with speed
v. Is it possible for the kinetic energy or the
momentum to be larger after a collision?
1) No; it is impossible
2) Yes; the kinetic energy can be larger
3) Yes; the momentum can be larger
4) Yes; both can be larger
Q32) Car One is traveling due north and Car Two is traveling due
east. After the collision shown, Car One rebounds due south.
Which of the numbered arrows is the only one that can represent
the final direction of Car Two
1) 1
2) 2
3) 3
4) 4
5) 5
Q33) An object of mass 3m, initially at rest, explodes breaking into two
fragments with masses m and 2m. Which one of the following statements
concerning the fragments after the explosion is true?
1) They may fly off at right angles.
2) They may fly off in the same direction.
3) The larger fragment will have twice the speed of the smaller fragment.
4) The smaller fragment will have twice the speed of the larger fragment.
5) The smaller fragment will have four times the speed of the larger
fragment.