AS Daily A Level Physics question
A skydiver has been falling for long enough that her speed has become constant. Which statement must be true at this moment?
Answer
The correct answer is C.
Correct: C — The upward air resistance equals the weight, so acceleration is zero. A claims weight is greater than air resistance; if that were true there would be a downward resultant and the speed would still increase. B suggests a nonzero resultant with constant speed, which contradicts zero acceleration required by Newton’s first law. C is correct because at terminal velocity the forces balance and the acceleration is zero. D is wrong because air resistance is not zero at terminal speed; it balances the weight.