# PHY Chapter 7

## Unlock all answers in this set

question
The work done in pushing a TV set a distance of 2 m with an average force of 20 N is A) 2 J. B) 10 J. C) 20 J. D) 40 J. E) 800 J.
D) 40 J
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The work you do when pushing a shopping cart twice as far while applying twice the force is A) half as much. B) twice as much. C) four times as much. D) the same amount
C) four times as much.
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No work is done by gravity on a bowling ball that rolls along a bowling alley because A) no force acts on the ball. B) little distance is covered by the ball. C) the force on the ball is at right angles to the ball's motion. D) the ball's speed remains constant.
C) the force on the ball is at right angles to the ball's motion.
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The unit kilowatt-hour is a unit of A) energy. B) momentum. C) power. D) time
A) energy
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Which task requires more work? A) lifting the 50-kg sack 2 meters B) lifting the 25-kg sack 4 meters C) both require the same D) need more information
C) both require the same
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The amount of work done on a heavy box carried by Nellie across a room at a constant speed A) depends on the weight of the box. B) depends on the distance walked. C) depends on both weight of the box and distance walked. D) is none. E) none of the above
D) is none.
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If you do work on a skateboard loaded with friends in one-third the usual time, you expend A) one third as much power. B) the usual power. C) three times the usual power. D) need more information.
C) three times the usual power.
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The power required to exert 4-N force over 3 meters in 2 seconds is A) 4 W. B) 6 W. C) 8 W. D) 12 W. E) none of the above
B) 6 W.
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An object has gravitational potential energy due to its A) speed. B) acceleration. C) momentum. D) location. E) none of the above
D) location.
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Relative to an initial height, an object raised twice as high has a gravitational potential energy A) half as much B) twice as much. C) four times as much. D) need more information
B) twice as much.
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When a drawn bow of potential energy 40 J is fired, the arrow will ideally have a kinetic energy A) less than 40 J. B) more than 40 J. C) of 40 J.
C) of 40 J.
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A clerk can lift cylindrical packages 1 meter vertically, or can roll them up a 2-meter-long ramp to the same elevation. With the ramp, the applied force required is about A) half as much. B) the same. C) twice as much. D) four times as much.
A) half as much.
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A 2-kg ball is held 4 m above the ground. Relative to the ground its potential energy is A) 6 J. B) 8 J. C) 32 J. D) 80 J. E) more than 80 J.
D) 80 J.
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A 2-kg box of taffy candy has 40 J of potential energy relative to the ground. Its height above the ground is A) 1 m. B) 2 m. C) 3 m. D) 4 m. E) none of the above
B) 2 m
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An object that has kinetic energy must be A) moving. B) falling. C) at an elevated position. D) at rest. E) none of the abov
A) moving.
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Two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has A) twice the kinetic energy. B) four times the kinetic energy. C) eight times the kinetic energy. D) none of the above
B) four times the kinetic energy.
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A melon is tossed straight upward with 100 J of kinetic energy. If air resistance is negligible the melon will return to its initial level with a kinetic energy of A) less than 100 J. B) more than 100 J. C) 100 J. D) need more information
C) 100 J
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Danny Diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of A) 10 J. B) 500 J. C) 510 J. D) 5000 J. E) more than 5000 J.
D) 5000 J.
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Which has greater kinetic energy? A) a car traveling at 30 km/hr B) a car of half the mass traveling at 60 km/hr C) both the same D) need more information
B) a car of half the mass traveling at 60 km/hr
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Neglecting air resistance, Sammy Smarts on a high ladder releases a ball that strikes the ground with 100 J of kinetic energy. If he were to instead throw the ball straight upward, it will soon reach the ground with a kinetic energy of A) less than 100 J. B) 100 J. C) more than 100 J.
B) 100 J
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If a Ping-Pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the Ping-Pong ball must be A) less than the golf ball. B) more than the golf ball. C) both the same D) need more information
B) more than the golf ball.
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Two identical particles move toward each other, one twice as fast as the other. Just before they collide, one has a kinetic energy of 25 J and the other 50 J. At this instant their total kinetic energy is A) 25 J. B) 50 J. C) 75 J. D) none of the above E) need more information
C) 75 J.
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When Joshua brakes his speeding bicycle to a stop, kinetic energy is transformed to A) potential energy. B) energy of motion. C) energy of rest. D) heat.
D) heat.
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A motorcycle moving at 50 km/h skids 10 m with locked brakes. How far will it skid with locked brakes when traveling at 150 km/h? A) 10 m B) 30 m C) 50 m D) 90 m
D) 90 m
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About 40 J is required to push a crate 4 m across a floor. If the push is in the same direction as the motion of the crate, the force on the crate is about A) 4 N. B) 10 N. C) 40 N. D) 160 N.
D) 160 N.
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Which requires the most amount of work by the brakes of a car? A) slowing down from 100 km/h to 70 km/h B) slowing down from 70 km/h to a stop C) equal amounts for both 26) 3
A) slowing down from 100 km/h to 70 km/h
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A ball rolling down an incline has its maximum potential energy at A) the top. B) a quarter of the way down. C) halfway down. D) the bottom.
A) the top
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The bob of a simple pendulum has its maximum kinetic energy at the A) top of its swing. B) bottom of its swing. C) midpoint between top and bottom. D) at all points along its path of swing.
B) bottom of its swing.
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A light aluminum ball and a heavy lead ball of the same size roll down an incline. When they are halfway down the incline, they will have identical A) kinetic energies. B) potential energies. C) momentum. D) inertias. E) none of the above
E) none of the above
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Strictly speaking, more fuel is consumed by your car if the air conditioner, headlights, or even a radio is turned on. This statement is A) false. B) true only if the car's engine is running. C) true.
C) true.
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A circus diver drops from a high pole into water far below. When he is halfway down A) his potential energy is halved. B) he has gained an amount of kinetic energy equal to half his initial potential energy. C) his kinetic energy and potential energy are equal. D) all of the above E) none of the above
D) all of the above
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Acrobat Bart at the circus drops vertically onto the end of a see-saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bart's dropping distance. Neglecting inefficiencies we see A) the masses of Art and Bart are equal. B) Art has half the mass of Bart. C) need more information
B) Art has half the mass of Bart.
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A 1-kg ball dropped from 2 m rebounds only 1.5 m after hitting the ground. The amount of energy converted to heat is about A) 0.5 J. B) 1.0 J. C) 1.5 J. D) 2.0 J. E) more than 2.0 J.
E) more than 2.0 J.
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A hydraulic press, like an inclined plane, is capable of increasing energy. A) sometimes true B) always false C) always true D) sometimes false
B) always false
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A hydraulic jack is used to lift objects such as automobiles. If the input force is 200 N over a distance of 1 meter, the output force over a distance of 0.1 meter is ideally A) 200 N. B) 500 N. C) 1000 N. D) 2000 N. E) none of the above
D) 2000 N
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Phil applies 100 N to a pulley system and raises a load one-tenth of his downward pull. Ideally, the weight of the load is A) 100 N. B) 1000 N. C) 10,000 N. D) more than 10,000 N
B) 1000 N.
question
A hydraulic press has its input piston depressed 20 centimeters while the output piston is raised 1 centimeter. A 1-newton input can lift a load of A) 1 N. B) 10 N. C) 15 N. D) 20 N. E) none of the above
D) 20 N.
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A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is A) 10%. B) 50%. C) 90%. D) 110%. E) none of the above
A) 10%
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A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is A) 10%. B) 20%. C) 50%. D) 80%. E) need more information
C) 50%.
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Earth's primary energy source is A) the Sun. B) fossil fuel. C) electricity. D) geothermal.
A) the Sun
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Hydro and wind power are indirect forms of A) solar energy. B) fossil fuels deep down. C) nuclear energy in Earth's interior. D) none of the above
A) solar energy.
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A machine that promises more energy output than input is A) a fantasy. B) commonplace in today's technology. C) a long-shot worth investing in.
A) a fantasy.
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The most concentrated form of energy is A) wind. B) fossil fuel. C) geothermal. D) nuclear
D) nuclear
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The exhaust product from a hydrogen fuel cell is A) carbon dioxide. B) methane. C) pure water. D) nitric acid
A) carbon dioxide.
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A primary difference between momentum and kinetic energy is A) momenta can cancel; kinetic energy cannot. B) kinetic energy can cancel; momenta cannot. C) either of the above depending on circumstances D) none of the above
A) momenta can cancel; kinetic energy cannot.
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Impulse involves the time that a force acts, whereas work involves the A) distance that a force acts. B) time and distance that a force acts. C) acceleration that a force produces.
A) distance that a force acts.
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A moving object has A) speed. B) velocity. C) momentum. D) energy. E) all of these