# How to calculate power

Question 11 pts

Power is defined as the

force exerted divided by the time of exertion.

work done divided by the time to do the work.

force exerted multiplied by the distance moved.

work done multiplied by the time to do the work.

Flag question: Question 2

Question 21 pts

If you exert 6 N across a distance of 2 m in 3 s you’ll deliver a power of

1 W

4 W

6 W

3 W

Flag question: Question 3

Question 31 pts

It takes 40 J to push a large crate 4 m across a floor. The force exerted on the crate is

10 N

4 N

160 N

40 N

Flag question: Question 4

Question 41 pts

A melon is projected into the air with 100 J of kinetic energy in the absence of air resistance. When it returns to its initial level its kinetic energy is

100 J.

less than 100 J.

more than 100 J.

Flag question: Question 5

Question 51 pts

The unit kilowatt-hour is a unit of

force

time

energy.

power.

Flag question: Question 6

Question 61 pts

A cat and a mouse run along a road with the same kinetic energy. The faster runner is the

cat.

not enough information

both run at the same speed.

mouse.

Flag question: Question 7

Question 71 pts

Which has greater kinetic energy, a car traveling at 30 km/h or another car of half the mass traveling at 60 km/h?

the 60-km/h car

the 30-km/h car

not enough information

both have the same kinetic energy

Flag question: Question 8

Question 81 pts

An object may have potential energy because of its

speed.

location.

acceleration.

inertia

Flag question: Question 9

Question 91 pts

If you do work on an object in half the time, your power output is

10 times

the same

twice

half

Flag question: Question 10

Question 101 pts

If you exert 100 J to lift a box in 50 s your power output is

4 W

2 W

1/4 W

1/2 W

Flag question: Question 11

Question 111 pts

An object that weighs 20 N has 40 J of potential energy relative to the ground. What is its height?

2 m

1 m

4 m

3 m

Flag question: Question 12

Question 121 pts

A shopping cart moves with a kinetic energy of 40 J. If it moves at twice the speed, its kinetic energy is

40 J

29 J

160 J

80 J

Flag question: Question 13

Question 131 pts

A 2-kg mass weighs 20 N and is held 4 m above the ground. Its potential energy relative to the ground is

20 J

80 J

8 J

60 J

Flag question: Question 14

Question 141 pts

Which requires more work: lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m?

lifting the 25-kg sack

not enough information

lifting the 50-kg sack

both require the same amount of work

Flag question: Question 15

Question 151 pts

Temperature of an object is the measure of ___________ of its particles.

potential energy

acceleration

kinetic energy

weight

Flag question: Question 16

Question 161 pts

The fact that a thermometer “takes its own temperature” illustrates

that molecules are constantly moving.

the difference between heat and thermal energy.

energy conservation.

thermal equilibrium.

Flag question: Question 17

Question 171 pts

The temperature of melting ice is