A machine takes in 500 J of energy and gives out 200 J of useful energy. What is its efficiency?
Answer and explanation
Correct answer: D. 40%
- Step 1: Efficiency .
- Step 2: .
Answer
40%.
Why not the others: 60%: that is the percentage of energy wasted. 300%: it subtracts the energies and reports joules as a percentage.
Practise more Energy.
Free questions with an explanation for every one, and full timed HKDSE (Hong Kong) mock tests.
More Energy questions
- A machine takes in 200 J of energy and gives out 160 J of useful energy. What is its efficiency?
- A machine takes in 400 J of energy and gives out 200 J of useful energy. What is its efficiency?
- A machine takes in 800 J of energy and gives out 640 J of useful energy. What is its efficiency?
- A constant force of 50 N pushes a box 2 m along a floor in the direction of the force. How much work is done?
- A force of 20 N acts at 60° to the horizontal on a box, moving it 3 m horizontally. How much work does the force do? ()
- A force of 120 N acts at 60° to the horizontal on a box, moving it 2 m horizontally. How much work does the force do? (…