AS Daily A Level Physics question
On level ground, a student fires a foam dart at 40° to the horizontal. Air resistance is negligible, and the dart lands at the same height it was launched. If the launch speed is doubled while keeping the angle the same, what happens to the horizontal range?
Answer
The correct answer is D.
Correct: D — It quadruples. A assumes the range is simply proportional to speed, but both horizontal speed and flight time each scale with speed, giving a squared effect. B confuses the dependence with a square-root change; range is not proportional to the square root of speed. C suggests a cube dependence, which is not the case for projectile range at fixed angle. D is correct because doubling launch speed doubles time of flight and doubles horizontal speed, so range = speed × time increases by 2 × 2 = 4.