Possibly useful information:






























For every question, also consider the following as a possible
answer:
e) none of the above
1. Which of the following has the largest momentum relative to
Earth?
a) a tightrope walker crossing Niagara Falls.
b) a truck speeding along a highway.
c) a Mack truck sitting in the parking lot. p = zero
d) the Science building on campus. p = zero
2. A moving object on which no
forces are acting will continue to move with constant
a) acceleration
b) impulse
c) momentum; constant velocity means constant momentum
d) all of these
3. Conservation of momentum is directly related to
a) Newton's First Law of Motion
b) Newton's Second Law of Motion
c) Newton's Third Law of Motion; F_{12} =  F_{21} leads to p_{12} =  p_{21} which leads toP_{tot,i} = p_{1,i} + p_{2,i} = p_{1,f} + p_{2,f} = P_{tot,if}d) International shortages of momentum :)
4. A rifle recoils from firing a bullet. The speed of the rifle's
recoil is small because the
a) force against the rifle is smaller than against the bullet.
b) momentum of the rifle is smaller than that of the bullet.
c) mass of the rifle is much larger than the mass of the bullet.
d) momentum of the rifle is larger than that of the bullet.
5. Two objects, A and B, have the same size and shape, but A is twice
as heavy as B. When they are dropped simultaneously from a tower,
they reach the ground at the same time, but A has a greater
a) speed
b) acceleration
c) momentump = m vv is the same for both
With a larger mass m, there will be a larger momentum p
d) all of the above
6. A 5 kg ball has a momentum of 30 kg m/s. What is the ball's
speed?
a) 3 m/s
b) 6 m/sp = m v30 kg m/s = (5 kg) ( 6 m/s)
v = 6 m/s
c) 15 m/s
d) 150 m/s
7. If two objects collide and do not stick together, their
total momentum after the collision is
a) less than
b) the same asMomentum is always conserved.c) greater than
their total momentum before the collision.
8. If two objects collide and stick together, their
total momentum after the collision is
a) less than
b) the same asMomentum is always conserved.c) greater than
their total momentum before the collision.
9. When two objects collide and stick together, this
type of collision is known as a
a) totally elastic collision.KE is also conserved in a totally elastic collision.The two objects do not stick together in a totally elastic collision.
b) totally inelastic collision.
Momentum is always conserved so momentum is conserved in this totally inelastic collision.c) totally natural collision.
d) totally impulsive collision.
10. Momentum is conserved in any collision. In a “totally
elastic collision” another quantity is also conserved. That
other conserved quantity is the
a) velocity, v
b) kinetic energy, KE
c) angular velocity, w
d) work, W
11. Work involves
a) mass multiplied by acceleration
b) mass multiplied by distance
c) force multiplied by distance
d) force multiplied by time
12. If you push an object twice as far while applying the same force you do
a) half as much work.
b) the same amount of work.
c) twice as much work.
d) four times as much work.
13. If you push an object just as far while applying twice the force you do
a) half as much work.
b) the same amount of work.
c) twice as much work.
d) four times as much work.
14. Exert 4 N for a distance of 3 m in 2 s and you deliver a power
of
a) 2.0 W
b) 4.0 W
c) 6.0 WP = W / tW = (4 N) (3 m) = 12 J
P = 12 J / 2 s
P = 6 W
Be careful; we are using P for "power" here and we have also used P for "momentum". Also, W means units of "watts" in the last equation here but W means "work" in the first two equations. Never use equations blindly. Equations are "shorthand" for longer, more involved statements.
d) 8.0 W
15. Exert 2,000 J of work in 50 s and your power output is
a) 5 W
b) 10 W
c) 20 W
d) 40 WP = W / tP = 2,000 J / 50 s
P = 40 W
16. An object is raised above the ground gaining a certain amount of
potential energy. If the same object is raised twice as high
it gains
a) half as much energy
b) the same amount of energy
c) twice as much energy
d) four times as much energy
17. An object that has kinetic energy must be
a) elevated
b) falling
c) movingKE = (^{1}/_{2}) m v^{2}d) at rest
18. An object that has potential energy may have this energy
because of its
a) speed
b) acceleration
c) momentum
d) position
19. When a car is braked to a stop, its kinetic energy is transformed
to
a) energy of motion
b) heat energy
c) stopping energy
d) potential energy
20. For which position above does the ball on the end of the string have the greatest gravitational potential energy?
a) PE_{g} = m g hAt position A, h, the height, is greatest.
21. For which position above does the ball on the end of the string have the greatest kinetic energy?
d) KE = (^{1}/_{2}) m v^{2}E_{tot} = KE + PEAt position D, the PE is smallest so KE will be greatest.
22. A 10 kg sack is lifted 2 meters in the same time as a 5 kg sack is lifted 4 meters. The power expended in raising the 10 kg sack compared to the power used to lift the 5 kg sack is
a) half as much
b) the sameThe work done is the same,W = (10 kg) (10 m/s^{2}) (2 m) = (5 kg) (10 m/s^{2}) (4 m) = W
P = W / t
Since the times are the same, the power is the same in the two cases.
c) twice as much
d) four times as much
23. A 3 kg mass is held 5 m above the ground. What is the approximate
potential energy of the mass with respect to the ground?
a) 15 J
b) 75 J
c) 150 JPE_{g} = m g h = (3 kg) (10 m/s^{2}) (5 m) = 150 Jd) 300 J
24. A 5 kg mass has 50 J of potential energy with respect to the
ground. Approximately how far is it located above the ground?
a) 0.5 m
b) 1 mPE_{g} = m g hPE_{g} = (5 kg) (10 m/s^{2}) (h) = 50 J
(50 kg m/s^{2}) (h) = 50 J
h = 1 m
c) 5 m
d) 10 m
25. A car moves 3 times as fast as another identical car.
Compared to the slower car, the faster car has
a) the same kinetic energy
b) 3 times the kinetic energy
c) 9 times the kinetic energyKE = (^{1}/_{2}) m v^{2}d) 27 times the kinetic energy
26. A car moving at 40 km/hr skids 20 m with locked brakes. How far
will the car skid with locked brakes if it is traveling at 120
km/hr?
a) 60 m
b) 90 m
c) 120 m
d) 180 mKE = (^{1}/_{2}) m v^{2}The velocity has increased by a factor of three.
That means the KE has increaseed by a factor of nine.
That means the stopping distance must also increase by a factor of nine.
distance = 20 m x 9 = 180 m
27. When a rifle is fired it recoils so both the bullet and rifle are
set in motion. The rifle and bullet ideally acquire equal but
opposite amounts of
a) kinetic energy
b) momentump_{12} =  p_{21}p_{rifle} =  p_{bulltet}
c) potential energy
d) all of the above
28. What does an object have when moving that it doesn`t have when at
rest?
a) momentumP = m vb) energy
c) mass
d) all of the above
29. If an object has kinetic energy, then it also must have
a) momentum
b) velocity
c) speed
d) all of the aboveKE = (^{1}/_{2}) m v^{2}
30. According to Kepler's laws, the paths of planets about the Sun
are
a) straight lines
b) parabolas
c) ellipses
d) hyperbolas
31. According to Newton, the greater the masses of interacting
objects, the
a) greater the force of gravity, by the product of the massesF_{g} = G Mm/r^{2}b) less the force of gravity
c) greater the force of gravity, by the square of the masses
d) less the force of gravity, inversely as the square of the masses
32. According to Newton, the greater the distance between masses of
interacting objects, the
a) greater the force of gravity, proportional to the distance
b) less the force of gravity, inversely as the distance
c) greater the force of gravity, proportional to the square of the distance
d) less the force of gravity, inversely as the square of the distanceF_{g} = G Mm/r^{2}
33. If the mass of Earth somehow increased with no
change in radius, your weight would
a) increaseF_{g} = G M m / r^{2}F_{g} = G M m / r^{2}
b) decrease
c) stay the same
34. If the radius of Earth somehow decreased with no
change in mass, your weight would
a) increaseF_{g} = G M m / r ^{2}F_{g} = G M m / r ^{2}
Dividing by a smaller number yields a larger number.
b) decrease
c) stay the same
35. If Earth's mass decreased to onethird its
original mass with no change in radius, then your weight would
a) decrease to oneninth its original value
b) decrease to onethird its original valueF_{g} = G Mm/r^{2}c) increase to nine times its original value
d) increase to three times its original value
36. The force of gravity acting on the Space Shuttle in orbit is
nearly
a) zero
b) equal to the weight of the Space Shuttle at Earth's surfaceF_{g} = G Mm/r^{2}The distance r at radius of the orbit for the Space Shuttle is nearly the same as at Earth's surface; it is only a few percent larger.
c) about onetenth its weight at Earth's surface
d) about oneone hundredth its weight at Earth's surface
37. A woman who normally weighs 500 N stands on top of a very tall
ladder so she is one Earth radius above the earth's surface. How much
would she weigh there?
a) zero
b) 125 NF_{g} = G Mm/r^{2}r is now twice Earth's radius
r = 2 R_{Earth}
F_{ladder} = ( ^{1}/_{4} ) F_{surface}
c) 250 N
d) 500 N
38. The force of gravity acts on all apples on an apple tree. Some
apples are twice as far from the ground as others. These twice
ashigh apples, for the same mass, have practically
a) onefourth the weight
b) onehalf the weight
c) the same weightF_{g} = G Mm/r^{2}r is the distance from the center of the Earth and that is essentially the same for all the apples; r = 6,000 km!
d) twice the weight
39. The planet Jupiter is about 300 times as massive as Earth, yet on
its surface you would weigh only about 3 times as much. This is
because
a) your mass is 100 times less on Jupiter.
b) Jupiter is significantly farther from the sun.
c) Jupiter's radius is 10 times Earth's radius.See the homework solution for details!d) you are 100 times more weightless there.
40. An industrial flywheel has a greater rotational inertia when most
of its mass is
a) nearer the axis
b) nearer the rim
c) spread out evenly
41. A hollow ring or hoop and a sphere roll down an incline starting
at the same time. The one to reach the bottom
first will be the
a) ring or hoop (this has the larger "rotational mass"
b) sphereWith a smaller "rotational mass" this one is easier to accelerate so it will move faster.c) neither; they both reach the bottom at the same time
42. Put a pipe over the end of a wrench when trying to turn a
stubborn nut on a bolt, to effectively make the wrench handle
twice as long, you'll increase the torque by a factor of
a) two
b) four
c) eight
d) sixteen
43. When a twirling ice skater extends her arms outward, her
rotational speed
a) increases
b) decreasesWhen her arms are extended, her "rotational mass" is larger.Angular momentum remains the same or is conserved.
Angular momentum = I
I = I
c) remains the same (ie, it is conserved).
44. To turn a stubborn screw, it is best to use a screwdriver that
has a handle that is
a) long and thin
b) thick or wide
c) yellow
d) slippery
45. A 1kg rock is suspended from the tip of a meter stick at the 0 cm mark so that the meter stick balances like a seesaw when the fulcrum is at the 25cm mark. From this information, what is the mass of the meter stick?
a) 0.25 kg
b) 0.50 kg
c) 1.00 kg.
d) 2.00 kg
46. A car travels in a circle with constant speed. The net
force on the car is
a) directed forward, in the direction of travel.
b) directed towards the center of the curveThis net force on an object moving in a circle is also known as the centripetal force.c) zero because the car is not accelerating.
d) directed outward, away from the center of the curve
47. A communications satellite appears stationary to an Earthbased
observer. The orbit such a satellite is in is called a
a) lowEarth orbit.
b) polar orbit.
c) geosynchronous orbit.It has a period of 24 hours and a radius of 40,000 km (or 25,000 mi).d) highEarth orbit.
48. As your kinetic energy is reduced to zero in an automobile crash,
use of seat belts means a stopping force is applied to your body over
a greater distance. This means the force on you is
a) less thanKE = W = F sW = F s = F s
b) the same as
c) more than
if you were not wearing seat belts.
49. As you climb the first hill of a roller coaster, work is done by
outside forces. At the top of that first hill, your velocity is
nearly zero and you have maximum
a) momentum.
b) kinetic energy.
c) potential energy.PE = m g hd) weight.
50. A diver does a double saumersalt and then extends his body so
that his rotation nearly stops before going into the water. This is
an example of conservation of
a) momentum.
b) kinetic energy.
c) potential energy.
d) angular momentum.
(C) 2003, Doug Davis; all rights reserved