AS Daily A Level Physics question
Two identical balls are thrown from the same height at the same angle to the horizontal. Ball B is thrown at twice the launch speed of ball A. Air resistance is negligible, and both land back at the launch height. Which statement must be true?
Answer
The correct answer is A.
Correct: A — Stone B’s maximum height is four times that of stone A, and its time of flight is twice as long. A because doubling the launch speed doubles the vertical component, so time up (and down) doubles, and maximum height depends on the square of the vertical launch speed, giving a factor of 2^2 = 4. B is wrong because the maximum height does not scale linearly with speed; it scales with the square of the vertical component, so it should be four times, not twice. C is wrong because the time of flight increases (it does not stay the same) when the vertical component is doubled, and the range would increase by a factor of four at the same angle, not two. D is wrong because the time of flight depends on the vertical launch component and therefore doubles, not remains unchanged.