Download Work, Power, Energy

Work, Power, Energy
1. A person lifts a box with a mass of 2.0 kg from the
6. Base your answer to the following question on the
ground to a shelf 0.5 m high. The work that gravity does
picture below, which represents a plane 10 m in length
on the box is equal to
with a coefficient of kinetic friction of 0.2, inclined at an
angle of 53º. A block of weight 30 N is placed at the top
A) –10 J B) –5 J C) 0 J
D) 5 J
E) 10 J
of the plane and allowed to slide down.
2. How much work is done lifting a 40 newton block 2
meters?
A) 20 joules
C) 40 joules
E) 80 joules
B) 38 joules
D) 42 joules
3. Which of the following is not a vector quantity?
A) Torque
C) Work
E) Force
B) Velocity
D) Momentum
4. A ball of mass 16 kg on the end of a string is spun at a
constant speed of 2.0 m/s in a horizontal circle with a
radius of 1 m. What is the work done by the centripetal
force during one complete revolution?
A) 0 J
B) 16 J
C) 32 J
D) 8 J
E) 4 J
5. A student pulls a block 3.0 meters along a horizontal
surface at constant velocity. The diagram below shows
the components of the force exerted on the block by the
student.
The velocity of the block after its 10 m slide down the
plane is most nearly
A) 8.2 m/s
C) 8.9 m/s
E) 10.0 m/s
B) 8.6 m/s
D) 9.7 m/s
7. A 100 W motor propels an object with a mass of 4 kg for
2 s from rest. Its final velocity will be
A) 5 m/s
C) 20 m/s
E) 100 m/s
B) 10 m/s
D) 40 m/s
8. An object at rest weighs 100 N on earth. It gains 100 J
of kinetic energy. What is its velocity?
A)
C)
E)
How much work is done against friction?
A) 6 J
B) 18 J
C) 24 J
D) 30 J
E) 42 J
m/s
m/s
m/s
B)
D)
m/s
m/s
Work, Power, Energy
9. A particle is fired straight up out of a cannon. Which of
the following graphs best represents its kinetic energy K
as a function of time t?
A)
B)
13. What is the velocity of a particle after falling 10 meters
if its initial velocity is 10 m/s?
A) 10
C) 20 m/s
E) 300 m/s
B) 10
D) 150 m/s
14. A pendulum of mass m on a massless string of length l
is displaced an angle . What is the maximum velocity
of the pendulum?
C)
D)
A)
C)
E)
B)
D)
E)
10. A car with kinetic energy 20,000 J travels along a
horizontal road. How much work is required to stop
the car in 5 s?
A) 0 J
C) 4,000 J
E) 16,000 J
B) 20,000 J
D) 8,000 J
11. What is the minimum velocity a toy car has to travel in
order to survive going through a loop of radius 0.2
meters if?
A)
m/s
C) 4 m/s
E) 16 m/s
B) 2 m/s
D) 8 m/s
12. Which of the following statements concerning a skier in
a valley is true if friction and air resistance are
negligible?
I. The skiers speed is maximum at the bottom of the
valley
II. The skiers speed is at a minimum at the top of the
valley
III. The skiers potential energy is zero at the top of the
valley
A) I only
C) I and II only
E) I, II and III
B) II only
D) II and III only
15. A block of mass 1 kg at rest slides down a frictionless
inclined plane as shown in the picture. The plane is
sloped at an angle of 30° relative to the ground. When
the block slides to the ground, its change in kinetic
energy is most nearly
A) +10J. B) –10J. C) +15J. D) –15J. E) +20J.
16. A bullet of mass m is shot into a spring with constant k.
If the spring depresses a distance x what was the
incident velocity of the bullet?
A)
B)
C)
D)
E)
17. A man standing a certain height above the ground
throws a rock of mass 1 kg straight up with an initial
velocity of 10 m/s. A few moments later, the rock hits
the ground with a kinetic energy of 450 J. If the man
dropped this rock from rest, how much kinetic energy
would it have right before it hits the ground?
A) 100 J B) 200 J C) 300 J D) 400 J E) 500 J
Work, Power, Energy
18. Units of energy include which of the following?
I. Newton-meter
II. Ampere-volt
III. Volt-coulomb
A) I only.
C) I and III only.
E) I, II, and III.
B) I and II only.
D) II and III only.
19. An object with a mass of 4 kg is released from rest at
the top of a ramp with length 10 m that makes an angle
of 30º with the horizontal. The coefficient of kinetic
friction between the block and the ramp is 0.4. The
speed the block will have when it has traveled 5 m
down the ramp is most nearly
A) 3.9 m/s
C) 7 m/s
E) 10.4 m/s
B) 5.6 m/s
D) 7.9 m/s
Base your answers to questions 20 and 21 on the
diagram below which shows a frictionless track.
21. Which of the following best describes the motion of an
object as it approaches point B, if it was released from
rest at the beginning of the track?
A) It is losing potential energy only.
B) It is gaining kinetic energy only.
C) It is gaining potential energy and gaining kinetic
energy
D) It is losing potential energy and gaining kinetic
energy
E) It is gaining heat energy, gaining kinetic energy,
and losing potential energy
22. Base your answer to the following question on the
following situation.
An object weighing 10 N swings at the end of a rope
that is 0.72 m long as a simple pendulum. At the bottom
of the of the swing, the tension in the string is 12 N.
What is the maximum height above its lowest point that
the object reaches?
A) 0.036 m
C) 0.072 m
E) 0.360 m
B) 0.060 m
D) 0.144 m
23. A student throws a stone upward at an angle of 30°.
Which statement best describes the stone at the highest
point that it reaches?
20. If an object is released at the beginning of the track,
which of the following is true at point E?
A)
B)
C)
D)
E)
It is in static equilibrium
It is losing kinetic energy
It is in dynamic equilibrium
There is a net force acting on the object
Its kinetic energy is 25 J
A)
B)
C)
D)
E)
Its acceleration is zero.
Its acceleration is at a maximum.
Its potential energy is at a minimum.
Its kinetic energy is at a minimum.
Its potential and kinetic energies are equal
Work, Power, Energy
24. Base your answer to the following question on the
26. Base your answer to the following question on the
following diagram, in which a ball of mass m is rolled
following information.
horizontally off a table of height h and lands a distance D from the edge of the table.
A roller coaster car starts at Point A and travels along a
frictionless slope traveling to Point E which is at a
slightly lower height.
If the initial horizontal velocity of the ball is represented
as the quantity v, what is the kinetic energy of the ball
right before it hits the ground?
If it can be assumed that the car has the same speed at
points A and E, which of the following statements is
true?
A) mgh
B) mv2
2
C) mv2 – 2mgh
2
D) mv2 + 2mgh
2
E) 2mgh – mv 2
2
A)
B)
C)
D)
The net work done in this system is 0 J.
The net work done in this system is positive.
The net work done in this system is negative.
The net work done in this system is 0 for the roller
coaster, but positive for the slope.
E) The net work done in this system is positive for the
roller coaster, but 0 for the slope.
25. Base your answer to the following question on the
picture below which shows a 3 kg block sliding 50 m
down a frictionless inclined plane dropping a distance
of 30 m.
What is the kinetic energy of the block at the end of the
drop?
A) 90 J
C) 500 J
E) 1500 J
B) 300 J
D) 900 J
27. An object is dropped off a cliff of height h and is
subjected to an average force of air resistance of F. If
the object has a mass of m, the kinetic energy it gains
during the fall will be equal to
A) mgh
C) mgh – F
E) mgh – Fh
B) mgh + F
D) mgh + Fh
28. A 3 kg object slides 90 meters down a frictionless
inclined plane dropping 45 meters. It then slides along
a horizontal surface with a coefficient of kinetic friction
of 1.0 until it stops. How far from the base of the
inclined plane does it stop?
A) 400 m
C) 500 m
E) 4,500 m
B) 450 m
D) 525 m
Work, Power, Energy
29. A baseball with mass 2 kg is thrown vertically upward
with a velocity of 10 m/s. If it lands with a velocity of
5 m/s, how much energy has been exhausted by air
resistance?
A) 5 Joules
C) 75 Joules
E) 150 Joules
B) 15 Joules
D) 125 Joules
30. A spring accelerates a 1 kg mass on ice. The mass
comes to a table top and after 1 meter it comes to a
stop. If the spring constant is 10 N/m and the spring is
depressed 5 cm, what is the coefficient of kinetic
friction?
A) 0.00125
C) 125
E) 1250
B) 0.0125
D) 250
31. A crate with mass 40 kg is pulled by a worker along a
surface at a constant velocity for 10 m. If the crate is
pulled for 5 s, and the coefficient of kinetic friction
between the surface and the crate is 0.5, the power
exerted by the worker over this time is most nearly
A) 20 W
C) 100 W
E) 400 W
B) 40 W
D) 200 W
32. A small space heater puts out 1,500 watts of heat on
average. How long will it take the space heater to add
3,750 joules of energy to the room?
A) 0.4 s
B) 2.5 s
C) 5 s
D) 1.25 s E) 6.25
33. a 60 kg climber reaches the top of a 40 meter cliff in 8
minutes. What is the average power consumed by the
climber?
A) 0.5 watts
C) 50 watts
E) 1920 watts
B) 5 watts
D) 300 watts
34. A skater is sliding on ice at a constant speed of 20 m/s
for 20 seconds. What is the average power consumed
by the skater?
A) 0 watts
C) 20 watts
E) 400 watts
B) 1 watt
D) 200 watts
35. Of the following, which is NOT a unit of power?
A)
B)
C)
D)
E)
Watt
Joule per second
Kilogram meter squared per second cubed
Kilowatt-hour
Ampere-volt
36. How much power is needed to lift a 100 kg block
vertically upward at a constant speed of 5 m/s?
A)
B)
C)
D)
E)
2,500 W
5,000 W
7,500 W
10,000 W
0 W because the object is at a constant velocity
37. A 500 N student expends an average power of 250 W to
climb a 6 m vertical rope at constant velocity. How
long does it take for the student to climb the rope?
A) 1 s
B) 2 s
C) 3 s
D) 6 s
E) 12 s
38. A 1 kg block slides down a 30 degree incline at a
constant 4 m/s. How much power is dissipated in the
form of heat by friction?
A) 0 watts
C) 20 watts
E) 400 watts
B) 8 watts
D) 40 watts
39. A boat motor exerts a force of 7,000 newtons of force
to maintain a speed of 7 m/s how much power does the
engine have?
A) 1,000 watts
C) 7,000 watts
E) 49,000 watts
B) 3,500 watts
D) 21,000 watts
40. A 300 N object is lifted 10 m by a crane at a constant
rate in 15 s. The average power expended to lift the
object is
A) 2 W
C) 200 W
E) 20,000 W
B) 20 W
D) 2,000 W