AS Daily A Level Physics question
Two shop hoists lift sacks vertically at constant speed through the same height of 4.0 m. Hoist 1 raises a 50 kg sack in 5.0 s. Hoist 2 raises a 75 kg sack in the same time. Air resistance is negligible. What is the ratio of their average mechanical power outputs, P2/P1?
Answer
The correct answer is A.
Correct: A — 1.5. A Power to the load over the same height and time is proportional to mass, so P2/P1 = 75/50 = 1.5. B Inverts the ratio, as if greater mass in the same time required less power. C Assumes power depends only on height and time, ignoring that lifting more mass needs more power. D Overstates the effect, as a 50% increase in mass does not double the power; it increases it by a factor of 1.5.