WAEC Physics 2015 Objective — Question 18

Question 18 of 50 from the West African Examinations Council (WAEC) Physics 2015 Objective paper, with the correct answer and a full explanation.

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

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

Explanation

With a velocity ratio of 6 (six pulleys), MA = Load/Effort and Efficiency = (MA/VR)×100%. So Effort = Load/(Efficiency×VR) = 100/(0.75×6) = 22.2 N.

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