AS Daily A Level Physics question
In a lab drop test, a small steel ball is released from rest from a platform 19.6 m above the floor and falls freely (air resistance negligible). Taking g = 9.81 m s−2, which statement about the times to fall the first 9.8 m compared with the last 9.8 m is correct? Support your choice with a brief estimate.
Answer
The correct answer is D.
Correct: D — The first half takes longer; roughly 1.4 s for the first 9.8 m and 0.6 s for the last 9.8 m. A assumes equal times for equal distances, but under constant acceleration distance grows with t^2; from 19.6 m the total time is about 2.0 s and the halfway-distance time is √2 ≈ 1.41 s, not 1.0 s. B reverses the timing; starting from rest makes the early part slower, not faster, so 0.6 s/1.4 s are swapped. C claims the later half is longer, but the ball is moving faster later, so the last 9.8 m is quicker (about 0.6 s), not ~1.4 s. D matches the estimate using s ≈ (1/2) g t^2 with g = 9.81 m s−2.