AS Daily A Level Physics question
A skydiver is falling at terminal speed with a small parachute, so the drag equals their weight W. They instantly switch to a larger canopy that, at the same speed, produces a drag force of 2.5 W. Which statement must be true about the acceleration immediately after the switch and how the speed changes next?
Answer
The correct answer is A.
Correct: A — Acceleration is 1.5 g upward; the speed then decreases towards a new, lower terminal speed. Since drag jumps to 2.5W at the same speed, the net force is 2.5W − W = 1.5W upward, giving an immediate acceleration of 1.5g upward; as speed falls, drag reduces until it equals W again at a lower terminal speed. B is wrong because it double-counts the net force as the acceleration (using 2.5g) and wrongly claims the speed falls to zero instead of approaching a new terminal value. C is wrong because it gives the wrong direction (downward) and magnitude; with drag > weight the net force must be upward and greater than g. D is wrong because although the initial 1.5g upward acceleration is correct, the subsequent behaviour is not: the speed must decrease to a lower terminal speed, not increase.