



 
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)(t^{2}). You'll need to solve for t of course. Cheers,  


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