When work is done on an object, energy is transferred. Power is the amount of work done in one second. Efficiency is a measure of how much useful energy is converted.
Which is a correct example of work being done?
An apple at rest on a table
A shelf holding up a book
A toy car being pushed across the floor
What are the correct units for work?
Work is measured in amps (A)
Work is measured in joules (J)
Work is measured in newtons (N)
How much work is done by a 10 N force pushing a box 4 m across the floor?
If a motor does 500 J of work to lift a 200 N weight, how high was the weight lifted?
Which of the following is a definition of power?
The amount of work done by a certain force
The energy transferred × time taken
The energy transferred ÷ time taken
A hair dryer transfers 10,000 J of energy in 4 s. What is its power?
A 60 W lamp is left on for 20 s. How much energy has been transferred?
What is one watt equal to?
One newton per second
One metre per second
One joule per second
The efficiency of a device is a measure of…
How much of the total input energy appears as useful output energy
How much of the useful output energy is conserved in other forms
How much of the total input energy is created from renewable sources
What is the correct formula for calculating efficiency?
Efficiency = useful output energy ÷ total input energy
Efficiency = total input energy ÷ useful output energy
Efficiency = useful input energy ÷ useful output energy