AS Daily A Level Physics question
In a lab test, a student drops a small steel ball from height h onto a soft mat, then repeats from height 4h. Ignore air resistance and take g = 9.81 m s^-2. Compared with the first drop, by what factor is the speed just before impact in the second drop?
Answer
The correct answer is B.
Correct: B — 2. With the same g and zero initial speed, the impact speed scales with the square root of the drop height, so the ratio is sqrt(4h/h) = sqrt(4) = 2. A assumes the speed is directly proportional to height, which is incorrect because speed does not increase linearly with height. B is the only option consistent with speed depending on the square root of height for free fall. C (~1.4) confuses quadrupling with doubling the height (sqrt(2) would apply to 2h, not 4h). D ignores that a longer fall under constant g leads to a greater impact speed.