Physics Principles and Problems 2009

Chapter 10: Energy, Work, and Simple Machines

Chapter Test Practice

1
An electric motor lifts an elevator 14.0 m in 22.5 s by exerting an upward force of 1.75×104 N. What power does the motor produce in kilowatts?
A)10.9 kW
B)1.09×104 kW
C)2.45×104 kW
D)245 kW
2

In the figure below, if the force exerted on the backpack is 20.0 N and the distance it acts over is 0.25 m, what is the change in kinetic energy of the backpack?

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A)2.5 J
B)5.0 J
C)4.0×101 J
D)8.0×101 J
3
If you exert a force on an object in the direction opposite to its motion, the kinetic energy of the object __________.
A)is zero
B)decreases
C)increases
D)remains constant
4
How much work does the force of gravity do when a 50.0-N object falls a distance of 10.0 m?
A)5.00×102 J
B)51.0 J
C)125 J
D)98.0 J
5
One __________ is one joule of energy transferred in one second.
A)calorie
B)newton
C)volt
D)watt
6
An airplane passenger carries a 300.0-N suitcase up the stairs, a displacement of 5.50 m vertically and 3.75 m horizontally. How much work does the passenger do?
A)1.13×103 J
B)1.65×102 J
C)2.78×103 J
D)1.65×103 J
7
A 1200.0-kg car speeds up from 16.0 m/s to 20.0 m/s. How much work was done on the car to increase its speed?
A)8.6×105 J
B)9.6×103 J
C)8.6×104 J
D)3.1×105 J
8

In the figure below, if the force exerted on a 3.0-kg backpack that is initally at rest is 20.0 N and the distance it acts over is 0.25 m, what is the final speed of the backpack?

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A)1.8 m/s
B)2.8 m/s
C)5.0 m/s
D)3.3 m/s
9
How much work does the force of gravity do on a 5.45-kg bowling ball that falls a distance of 0.755 m?
A)40.3 J
B)71.2 J
C)4.11 J
D)262 J
10
The equation for calculating work when there is an angle between force and displacement is __________.
A)W = Fd cos Δ
B)W = F/m
C)W = Fd
D)W = FΔKE
11
The energy of an object resulting from motion is __________ energy.
A)potential
B)kinetic
C)mechanical
D)thermal
12
A 16.8-kg boy is riding in a 4.50-kg wagon. A 14.0-kg girl pushes the wagon and exerts a constant force of 2.60 N over a distance of 3.50 m. How much work does the girl do pushing the wagon?
A)9.10 J
B)127 J
C)0.26 J
D)66.4 J
13
A student lifts a box of books that weighs 215 N. The box is lifted 1.75 m. How much work does the student do on the box?
A)38.4 J
B)217 J
C)123 J
D)376 J
14
Energy is defined as __________.
A)power
B)the ability of an object to produce change in the environment or itself
C)motion
D)the effort required to perform work
15
A student lifts a box of books that weighs 215 N. The box is lifted 1.75 m. What is the change in energy of the box?
A)38.4 J
B)376 J
C)225 J
D)123 J
16
The work-energy theorem states that __________.
A)when a machine works at 100 percent efficiency, the energy of the system remains constant
B)when work is done at a rate of one joule per second, the power produced is one watt
C)when work is done on an object, a change in kinetic energy results.
D)effort is required to resist a change in the energy of a system
17
A joule is __________.
A)1 N·s
B)1 N·m/s
C)1 N·m
D)1 Fr/Fe
18
The unit for kinetic energy is the __________.
A)ampere
B)volt
C)joule
D)watt
19
A steel ball with mass 5.0 kg is at rest on a smooth, level surface. A constant force acts on it through a distance of 10.0 m causing it to roll at 25 m/s. What is the magnitude of the force?
A)1.6×102 N
B)1.6×103 N
C)4.9 N
D)6.3 N
20
A rope is used to pull a metal box 12.0 m across the floor with a force of 456 N. The rope is held at an angle of 52.0° with the floor. How much work does the puller do?
A)5.47×103 J
B)4.31×103 J
C)3.37×103 J
D)3.37×102 J
21
A sailor pulls a boat 15.0 m along a dock using a rope that makes a 45.0° angle with the horizontal. How much work does the sailor do on the boat if he exerts a force of 185 N on the rope?
A)1.96×103 J
B)1.59×103 J
C)1.96×102 J
D)2.78×103 J
22
A 1200.0-kg car speeds up from 16.0 m/s to 20.0 m/s. What were its initial and final energies?
A)initial 4.80×105 J, final 3.07×105 J
B)initial 2.40×105 J, final 1.54×105 J
C)initial 1.54×105 J, final 2.40×105 J
D)initial 3.07×105 J, final 4.80×105 J
23
A forklift raises a box 2.5 m doing 8.7 kJ of work on it. What is the mass of the box?
A)3.6×103 kg
B)3.5×103 kg
C)7.2×102 kg
D)3.6×102 kg
24
The equation for work is __________.
A)W = Fd
B)W = FΔKE
C)W = ma
D)W = F/m
25
A rifle can shoot a 4.20-g bullet at a speed of 965 m/s. What is the kinetic energy of the bullet as it leaves the rifle?
A)1.96×106 J
B)2.03 J
C)1.96×103 J
D)2.03×103 J
26
Which of the following has the greatest kinetic energy, a 35.0-g bullet traveling at 1.20×103 m/s, a 35.0-kg cheetah running at 30 m/s, an 875-kg car traveling at 5 m/s, or a 148-g pitched baseball moving at 45 m/s?
A)bullet
B)cheetah
C)car
D)baseball
27
A 16.8-kg boy is riding in a 4.50-kg wagon. A 14.0-kg girl pushes the wagon and exerts a constant force of 2.60 N over a distance of 3.50 m. What is the change in energy of the boy and the wagon?
A)9.10 J
B)12.8 J
C)25.5 J
D)47.6 J
28
A hydrolic lift raises a 1.14×103-kg car a distance of 2.4 m. If the car is lifted in 47 s, how much power does the lift produce?
A)570 kW
B)290 W
C)570 W
D)58.2 W
29
__________ is the rate of doing work.
A)Energy
B)Force
C)Power
D)Effort
30
The ratio of resistance force to effort force is called the __________.
A)torque
B)mechanical advantage
C)power
D)efficiency
31

If the machine below is ideal and an effort force of 7.0 N just lifts a 14.0 N box situated 0.75 m from the pivot, what is the distance from the pivot point to where the effort force is exerted?

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A)2.0 m
B)0.38 m
C)1.5 m
D)65 m
32

If the efficiency of the pulley system bellow is 95 percent, what effort force must be exerted to lift a 20.0 N box at constant velocity?

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A)20 N
B)19 N
C)22 N
D)21 N
33
The __________ of a machine is defined as the ratio of output work to input work.
A)IMA
B)mechanical advantage
C)efficiency
D)reliability
34
The rear wheel of a bicycle has a radius of 38.5 cm and has a gear with a radius of 4.75 cm. When the chain is pulled with a force of 175 N, the wheel rim moves 18.0 cm. The efficiency of this part of the bike is 95.0 percent. How far was the chain pulled to move the rim that amount?
A)1.45×102 cm
B)1.45 cm
C)2.12 cm
D)2.21 cm
35
The force exerted by a machine is called the __________.
A)mechanical advantage
B)effort force
C)mechanical force
D)resistance force
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