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46 Cards in this Set
- Front
- Back
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In physics, work is defined as...
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force times distance.
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If you two loads up one story, how much work do you do compared to lifting just one load up one story?
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twice as much.
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If you one load up two stories, how much work do you do compared to lifting one load up only one story?
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twice as much.
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If Nellie Newton pushes an object with twice the force for twice the distance, she does
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four times the work
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The unit of work is the...
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joule.
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Power is defined as the...
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work done on an object divided by the time taken to do the work.
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The unit of power is the...
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watt.
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Potential energy is the energy an object has because of its...
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location.
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The amount of potential energy possessed by an elevated object is equal to...
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the work done in lifting it.
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Kinetic energy of an object is equal to...
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one half the product of its mass times its speed squared.
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How much farther will a car traveling at 100 km/s skid than the car traveling at 50 km/s
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four times as far
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An arrow in a bow has 70-J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot...
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70-J.
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Energy is changed from one form to another with no net loss or gain.
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Always true
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As a pendulum swings back and forth ....
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Potential energy is transformed into kinetic energy. At the lowest part of the swing, its energy is all kinetic. Kinetic energy is transformed into potential energy. At the end points of its swing, its energy is all potential. (all of the above)
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When a car's speed triples, its kinetic energy..
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increases by nine times.
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A job is done slowly, and an identical job is one quickly. Both jobs require the same amount of work but different amounts of...
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power.
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Which requires more work: lifting a 70-kg sack vertically 2 meters or lifting a 35-kg sack vertically 4 meters?
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Both require the same amount of work.
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A ball is thrown into the air with 100-J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is...
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less than 100-J.
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Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h?
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The 60 km/h car.
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An object at rest may have...
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energy.
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How many joules of work are done on a box when a force of 25 N pushes it 3 m?
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75 J
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How much power is required to do 40 J of work on an object in 5 seconds?
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8W
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How much work is done on a 60-N box of books that you carry horizontally across a 6-m room?
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0 J
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How much work is done on a 20-N crate that you lift 2 m?
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40 J
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How much power is expended if you lift a 60 N crate 10 meters in 1 second?
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600 W
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Suppose a moving car has 3000 J of kinetic energy. If the car's speed doubles, how much kinetic energy will it then have?
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12,000 J
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It takes 80 J to push a large box 8 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
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10 N
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A 60 N object moves 1 m/s. Its kinetic energy is...
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3 J
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Mechanical energy can be in the form of
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either kinetic energy or potential energy
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In physics, the amount of work done on an object is the product of the force exerted on the object times the time the object moves
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F
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The unit of work is called the Joule
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T
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The rate at which work is done is called energy
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F
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The unit of power is the watt.
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T
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The rate at which work is done is called power
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T
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The energy an object has by virtue of its location is its potential energy.
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T
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The energy of an object has by virtue of its motion it its kinetic energy.
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T
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More power is needed to carry a heavy suitcase slowly up a flight of stairs then carry the suitcase quickly up the same flight of stairs.
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F
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Energy transforms from one form to another with no net loss or gain
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T
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What is the work done in lifting 60 kg of blocks to a height of 20 m?
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12,000 J
Work = Force x Distance = (mass x acceleration) x Distance; acceleration= gravity = 10 m/s2W = 60 kg x 10 m/s2x 20mW= 12,000J |
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What is the work done in raising a 20-kg block 5 m vertically?
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1000 J
Work = Force x Distance = (mass x acceleration) x DistanceW = 20 kg x 10 m/s2x 5mW= 1,000J |
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What amount of work is done on a chair that is pushed 9 m across a floor by a horizontal 30-N net force?
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270 J
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A toy cart moves with a kinetic energy of 10 J. If its speed is doubled, what will its kinetic energy be?
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40 J
Kinetic Energy (KE) = ½ mv^2KE = ½ m (2v^2) = 4 x KE KE = 4 x 10 J = 40 J |
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In raising a 3000-N piano with a pulley system, it is noted that for every 2 m of rope pulled down, the piano rises 0.2 m. Ideally, what force is needed to lift the piano?
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300 N
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A car traveling at 50 km/h will skid 20 m when its brakes are locked. If the same car is traveling at 150 km/h, what will be its skidding distance?
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180 m
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A couch potato might consume 7 million J of energy in a day. What is this rate of energy consumption in watts?
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81 W
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A 30-kg girl runs up the staircase to a floor 5 m higher in 8 seconds. What is her power output?
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187.5 W
Power = Work/Time; Work = Force x Distance = (mass x acceleration) x DistancePower = (30 kg x 10 m/s^2 x 5m)/ 8sW = 187.5 W |
