WAEC Physics 2024 Objective — Question 28
Question 28 of 50 from the West African Examinations Council (WAEC) Physics 2024 Objective paper, with the correct answer and a full explanation.
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28. A boy of mass 40 kg jumps off a stationary skateboard and moves horizontally with a speed of 1.5 ms^-1 while the skateboard moves in the opposite direction with a speed of 20 ms^-1. Calculate the mass of the skateboard.
- A. 60 kg
- B. 40 kg
- C. 3 kgCorrect
- D. 2 kg
Explanation
By conservation of momentum, total initial momentum=0 (both at rest). 0=mb.vb+ms.vs = (40x1.5)+ms(-20). 20ms=60. ms=3kg.
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