A2 Daily A Level Physics question
In a lab demo, a low-friction trolley moves at a steady horizontal speed u past a drop point and releases a small steel ball from a height h above the floor. Air resistance is negligible and take g = 9.81 m s^-2. The demo is repeated from the same height with the trolley’s speed doubled to 2u. Which statement must be true when comparing the two drops, as judged by an observer on the floor?
Answer
The correct answer is D.
Correct: D — The time to hit the floor is unchanged and the horizontal distance before impact doubles. The vertical fall time depends only on height and g, so it is unchanged; doubling the horizontal speed doubles the horizontal distance covered in that same time. A The vertical fall time does not depend on horizontal speed, so it does not double; only the horizontal distance would double. B The fall time does not halve because the vertical motion (height and g) is unchanged; the horizontal distance would not stay the same—it would increase. C The horizontal distance cannot be unchanged because the horizontal speed is doubled while the time is the same. D Matches independence of components: same fall time, doubled horizontal range.