Physics

Grade-9

Easy

Question

# A construction worker puts 20 J of energy in to one strike of his hammer on the head of a nail. The energy transferred to the act driving the nail in to the wood is 8.0 J. What is his efficiency of hammering?

- 32%
- 160%
- 1/32%
- 1/160%

## The correct answer is: 32%

- Efficiency (%) = (useful energy output ÷ energy input) × 100

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