A wheel and an axle is used to raise a load whose weight is 800N...

JAMB 2014

A wheel and an axle is used to raise a load whose weight is 800N when an effort of 250N is applied. If the radii of the wheel and axle are 800mm and 200mm respectively, the efficiency of the machine is

A. 90%
B. 80%
C. 85%
D. 87%

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Correct Answer: Option B

Explanation

VR = 800/200 = 4
\(Efficiency = \frac{MA}{VR} \times \frac{100}{1}\)

\(Efficiency = \frac{L}{E} \times \frac{1}{VR} \times \frac{100}{1}\)

\(Efficiency = \frac{800}{250} \times \frac{1}{4} \times \frac{100}{1}\)

= 78.74%
= 80%

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