Work, Power and Efficiency

To find the amount of work done on an object, you must

• divide force and power

• divide force and distance

• multiply force and power

• multiply force and distance

Which of the following is NOT an example of work being done?

• Lifting a weight above your head

• Carrying a box up the stairs

• Pushing furniture across the room

• Pushing downward on an unmoving table

Power is defined as

• How much work is done

• The rate at which work is done

• How many things are plugged into an outlet

• The rate at which energy is used

Tags

NGSS.MS-PS3-5

NGSS.MS-PS3-4

We can calculate power by

• multiplying work and time

• dividing work by time

• multiplying force and work

• dividing force by work

How much work is done by lifting an object with a weight of 250 N a total of 2 m off the ground?

• 125 J

• 125 W

• 500 W

• 500 J

An engine does 300 J of work in 10 seconds. How much power did it use?

• 3000 N

• 3000 W

• 30 W

• 30 J

If a car weighs 3000 N and drives a distance of 10 m in 2 seconds, how much power does it use?

• 1,500 J

• 60,000 W

• 15,000 W

• 6,000 J

Tags

NGSS.MS-PS3-5

Efficiency is a measure of

• how much work is done per second

• how much work is output versus to how much work is input

• how much power is used per second

• how much power is output versus how much power is input

What is the efficiency of a car that has enough fuel to drive 600 miles, but only actually drives 150 miles?

• 25%

• 4%

• 400

• .25

Why we get more tired running up the stairs than we do walking up the stairs?

• We do more work

• We use more power

• Because we use more force

• Because we travel a longer distance

Tags

NGSS.HS-PS2-1