Math CentralQuandaries & Queries


Question from anoi90, a student:

a small parachute dropped from a 30.0 m high sliff falls with a constant velocity of 1.20 m/s. 20.0 s after the parachute is dropped, a stone is dropped from a cliff. Will the stone catch up the parachute before it reaches the ground? (Include numerical proof!)

Hi there.

You have to calculate two times and compare them, looking for a difference of 20 seconds or more.

The parachute falls at a constant vertical velocity, so you can use the equation t = d / v (where t is time, d is distance and v is velocity).

The stone falls at a constant vertical acceleration beginning from rest, so you can use the equation d = 1/2(a)(t2). You'll need to solve for t of course.

Stephen La Rocque.

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