AS Daily A Level Physics question
In a drop-timer lab, a steel ball released from rest falls 1.20 m and the measured time is 0.495 s. The setup is repeated from 2.40 m with air resistance negligible and g = 9.81 m s^-2. Using proportional reasoning rather than re-deriving equations, which predicted impact time is most consistent with the physics?
Answer
The correct answer is B.
Correct: B — 0.70 s. Doubling the drop height multiplies the time by √2 because, from rest under constant g, time scales with the square root of height, so 0.495 × √2 ≈ 0.70 s. A assumes time doubles with height (t ∝ h), which is incorrect for constant acceleration. B applies the √ relation correctly. C implies almost no change, ignoring that a greater height must give a longer time. D wrongly applies an inverse-root idea (t ∝ 1/√h), which would predict a shorter time when the height is increased.