Question

A boy on a cliff of 480 m high drops a stone.One second later he throw a second stone after the first.They both hit the ground at the same time.With what velocity does he throw the second stone?
Take g=10

Answer 1

s = ut + 1/2at^2 
u =0 in first part 
so 480 = 1/2 x 10 x t^2 
480 = 5t^2 
t = 9.8s 

part 2 throwing stone t = 1 second less = 8.8s 
s = ut + 1/2at^2 
where s = 480, t = 8.8 (approx) 
480 = 8.8u + 5 x 8.8^2 
8.8u =480 - 387 
u = 10.5 m/s 

Answer 2

Answer:

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