Work and Power
The transfer of energy to an object by the application of a force that causes the object to move in the direction of the force is...
What is work
The capacity to do work is...
What is energy
____ readily changes from one form to another.
What is energy
How much work is done by a person who uses a horizontal force of 25 N to move a desk 5.0 m?
W = Fd = (25 N)(5.0 m) = 125 J
A quantity that measures the rate at which work is done or energy is transformed is...
What is power
Name a type of energy
What is the source of energy in sunshine?
solar
While rowing across the lake during a race, John does 4,200 J of work on the oars in 60.0 s. What is his power output in watts?
P = W/t = (4,200 J)/(60.0 s) = 70.0 W
Two students who weigh the same start at the same ground floor location at the same time to go to the same classroom by different routes. If they arrive at different times, which student will have expended more power?
The energy of an object due to the object's motion is...
What is kinetic energy
Why is "close the door, you're letting the cold in!" considered wrong in terms of energy conservation?
Only heat can be transferred, heat is leaving the room and what's felt is the absence of heat
A 70 kg rock climber ascends a cliff. What is the climber's gravitational potential energy at a point 20 m above the base of the cliff?
PE = mgh = (70 kg)(9.8 m/s2)(20 m) = 13720 J
Which requires more work - lifting a 50 kg sack vertically 2 m or lifting a 25 kg sack vertically for 4?
They require the same
The sum of object's kinetic and potential energies is...
What is mechanical energy
If a 2 kg and 4 kg marble are rolled down a ramp from some height towards a container the _______ marble will move the container farther because it possess more _________ energy as it approaches the end of the ramp.
heavier marble / kinetic
What is the kinetic energy of a 40 kg cheetah running at 30 m/s?
KE = (1/2)mv2 = (1/2)(40 kg)(30 m/s)2 = 18000 J
If two sacks, one twice as heavy as the other, are lifted the same vertical distances in the same time, how does the power required for each compare?
Power is doubled
As a roller coaster car travels through the course, the trade off between kinetic energy and potential energy will be...
What is equal
A person with a mass of 60 kg jumps in the air. If the gravitational potential energy is 1,470 J at the highest point, how far they jump?
2.5 m
A 60 kg woman runs up a staircase 15 m high (vertically) in 20 s. How much power does she expend? What's her horsepower rating (1 hp = 746 W)
450 W, 0.6 hp