WAEC Physics 2021 Objective — Question 15
Question 15 of 50 from the West African Examinations Council (WAEC) Physics 2021 Objective paper, with the correct answer and a full explanation.
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15. The handle of a screw jack is 35 cm long and the pitch of the screw is 0.5 cm. What force must be applied at the end of the handle to lift a load of 2000 N if the efficiency of the jack is 30%? [π=22/7]
- A. 152.0 N
- B. 132.0 N
- C. 15.2 NCorrect
- D. 440.0 N
Explanation
Velocity ratio = 2πa/p = 2π(35)/0.5 = 440. Mechanical advantage = efficiency×VR = 0.3×440 = 132. Effort = Load/M.A. = 2000/132 ≈ 15.2 N.
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