# Physics Chapter 7

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four times as much
The work you do when pushing a shopping cart twice as far while applying twice the force is
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twice as much work
A 1000-kg car and a 2000-kg car are hoisted to the same height. Raising the more massive car requires...
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energy
The unit kilowatt-hour is a unit of
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C
Which task requires more work? A. lifting the 50-kg sack 2 meters, B. lifting the 25-kg sack 4 meters, or C. both require the same
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three times the usual power
If you do work on a skateboard loaded with friends in one-third the usual time, you expend
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2 W
The power expended doing 100 J of work in 50 s is
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6 W
The power required to exert 4-N force over 3 meters in 2 seconds is
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the same
Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is
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50 W
A toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed using 1000 J of work, is
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twice as much
Relative to an initial height, an object raised twice as high has a gravitational potential energy
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twice as much
A crate of grapes lifted 10 meters gains 200 J of potential energy. If the same crate is instead lifted 20 meters, its gain in potential energy is
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of 40 J
When a drawn bow of potential energy 40 J is fired, the arrow will ideally have a kinetic energy
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2 m
A 2-kg box of taffy candy has 40 J of potential energy relative to the ground. Its height above the ground is
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D. All of the above
The ram of a pile driver drops onto the top of an iron beam, driving it partway into the ground. The distance that the beam sinks into the ground depends on the A. kinetic energy of the ram when it first hits the beam B. initial potential energy of the ram. C. initial height of the ram. D. all of the above
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moving
An object that has kinetic energy must be
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four
Two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has _______ times the kinetic energy
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100 J
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
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5000 J
Danny Diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of
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75 J
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
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heat
When Joshua brakes his speeding bicycle to a stop, kinetic energy is transformed to
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twice as far
Two identical arrows, one with twice the kinetic energy of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates...
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the top
A ball rolling down an incline has its maximum potential energy at
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the bottom
A ball rolling down an incline has its maximum kinetic energy at
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bottom of its swing
The bob of a simple pendulum has its maximum kinetic energy at the
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the same as its potential energy
After rolling halfway down an incline, a marble's kinetic energy is
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halfway down
A block of ice sliding down an incline has half its maximum kinetic energy
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slowed
When wind encounters a wind turbine that produces energy, wind speed on the downside of the blades is
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true
Strictly speaking, more fuel is consumed by your car if the air conditioner, headlights, or even a radio is turned on. This statement is...T/F
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Art has half the mass of Bart
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
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true
When properly used, a hydraulic press, like a wheel and axle, is capable of multiplying force input. T/F
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2000 N
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...
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1000 N
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
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10%
A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is...
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50%
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...
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40 km
A miracle car with a 100% efficient engine burns fuel having a 40- megajoules-per-liter energy content. If air drag and overall frictional forces at highway speeds totals 1000 N, what distance per liter can be...
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the sun
Earth's primary energy source is
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solar energy
Hydro and wind power are indirect forms of...
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a fantasy
A machine that promises more energy output than input is
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nuclear
The most concentrated form of energy is
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electricity and heat
Solar power is commonly used to produce
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distance a force acts