A2 Daily A Level Physics question
In a sports hall, two identical foam balls are launched from the same height at the same speed, one at 30° and one at 60° above the horizontal. Air resistance is negligible and both land back at the same height. Which statement must be true?
Answer
The correct answer is D.
Correct: D — The 60° shot stays in the air √3 times as long, and both land with the same speed. The time aloft is set by the vertical component only, which scales with sinθ, so T60/T30 = sin60°/sin30° = (√3/2)/(1/2) = √3; with no air resistance and equal launch/landing height, the speed just before landing equals the launch speed for both. A The times are not the same because the vertical component differs; also, longer upward motion does not reduce the final speed when returning to the same height without air resistance. B Time does not scale linearly with angle (it depends on sinθ), and the final speed is not higher because mechanical energy is conserved in flight. C The √3 time factor is right, but claiming a higher landing speed is wrong since the speed on return to the same height matches the launch speed in ideal projectile motion. D This combines the correct proportional time change from the vertical component with the correct conclusion about equal landing speeds from energy/symmetry.