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BECE Science 2019 Paper

Question : 3

Total: 40

Solution:

Concept:

No practical machine can convert all input energy into useful output work because some energy is lost, mainly as heat due to friction.

Explanation:

Efficiency is given by:

\text{Efficiency} = \frac{\text{Useful work output}}{\text{Total work input}} \times 100\%

In all real machines, the useful work output is always less than the total work input due to energy losses.

Therefore, efficiency is always less than

100\%

Answer:

B. less than 100%

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