The diagram above illustrates a block ans tackle pulley system in which an effort E...

WAEC 2015

The diagram above illustrates a block ans tackle pulley system in which an effort E supports a load of 100.0N. If the efficiency of the machine is 75%, calculate the value of E

A. 22.2N
B. 38.0N
C. 67.0N
D. 75.0N

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Correct Answer: Option A

Explanation

Given; VR = 6, e = 75%, MA = ?

e = \(\frac{\text{MA}}{\text{VR}} \times \frac{100}{1}\)

MA =\(\frac{75 \times 6}{10}\)

MA = \(\frac{9}{2}\)

MA = \(\frac{L}{E} = \frac{100}{E}\)

\(\frac{9}{2} = \frac{100}{E}\)

9E = 100

E = \(\frac{200}{9}\)

= 22.2N

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