Energy Test
As a pendulum swings back and forth...
All of the below... At the end points of its swing, its energy is all potential. At the lowest part of its swing, its energy is all kinetic. Kinetic energy is transformed into potential energy. Potential energy is transformed into kinetic energy.
Energy is changed from one form to another with no net loss or gain.
Always true.
How much work is done on a 60 N box of books that you carry horizontally across a 6 m room?
0 J.
At what height does a 1000 kg mass have a potential energy of 1 J relative to the ground?
1/1000
Mechanical energy can be in the form of...
Both kinetic and potential energy.
Which requires more work: lifting a 70 kg sack vertically 2 meters or lifting a 35 kg sack vertically 4 meters?
Both require the same amount of work.
A pulley system can...
Both... Change the direction of a force. Multiply the force.
The ratio of useful work output to total work input is called the...
Efficiency.
What's the definition of kinetic energy?
Energy that a body possesses by virtue of being in motion.
An object at rest may have...
Energy.
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. T or F?
False.
More power is needed to carry a heavy suitcase slowly up a flight of stairs than to carry the suitcase quickly up the same flight of stairs. T or F?
False.
The rate at which work is done is called energy. T or F?
False.
The ratio of output force to input force for a simple machine is its efficiency. T or F?
False.
The ratio of useful work output to total work input is mechanical advantage. T or F?
False.
In physics, work is defined as...
Force times distance.
If Nellie Newton pushes an object with twice the force for twice the distance, she does...
Four times the work.
If possible, determine the power expended when a barbell is raised 5 m in 2 s.
Impossible; not possible
When a car's speed triples, its kinetic energy...
Increases by nine times.
The unit of work is the...
Joule (J).
Potential energy is the energy an object has because of its...
Location.
The ratio of output force to input force of a simple machine is called...
Mechanical advantage.
An object that has kinetic energy must be...
Moving.
A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives more kinetic energy is...
Neither one- they receive the same amount of kinetic energy.
Kinetic energy of an object is equal to...
One half the product of its mass times its speed squared.
A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of...
Power.
Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h?
The 60 km/h car.
What's the definition of potential energy?
The energy possessed by a body by virtue of its position.
The amount of potential energy possessed by an elevated object is equal to...
The work done in lifting it.
Energy transforms from one form to another with no net loss or gain. T or F?
True.
The energy an object has by virtue of its location is its potential energy. T or F?
True.
The energy of an object has by virtue of its motion is its kinetic energy. T or F?
True.
The rate at which work is done is called power. T or F?
True.
The unit of power is the watt. T or F?
True.
The unit of work is called the joule. T or F?
True.
Using an inclined plane is an effective way to life a heavy object that you otherwise couldn't do. T or F?
True.
If you lift one load up two stories, how much work do you do compared to lifting one load up one story?
Twice as much.
If you lift two loads up one story, how much work do you do compared to lifting just one load up one story?
Twice as much.
The unit of power is the...
Watt (W).
Power is defined as the...
Work done on an object divided by the time taken to do the work.
All simple machines ideally work on the principle that...
Work input equals work output.
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?
10 N.
A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is...
10%.
What is the work done in raising a 20 kg block 5 m vertically?
1000 J.
Suppose a moving car has 3000 J of kinetic energy. If the car's speed doubles, how much kinetic energy will it have then?
12,000 J.
What is the work done in lifting 60 kg of blocks to a height of 20 m?
12,000 J.
A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 140 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball his the ground?
140 J.
What amount of work can a 600 W motor do in 4 minutes?
144,000 J.
A 30 kg girl runs up the staircase to a floor 5 m higher in 8 seconds. What is her power output?
188 watts.
A 60 N object moves at 1 m/s. Its kinetic energy is...
3 J.
A toy cart moves with a kinetic energy of 10 J. If its speed doubled, what will its kinetic energy be?
40 J.
How much work is done on a 20 N crate that you lift 2 m?
40 J.
How much power is expended if you lift a 60 N crate 10 meters in 1 second?
600 W.
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 is had been shot?
70 J.
How many joules of work are done on a box when a force of 25 N pushes it at 3 m?
75 J.
How much power is required to do 40 J of work on an object in 5 seconds?
8 W.