Question

A boy on cliff 49m high drops a stone.One second later,he throws a second stone after the first.They both hit the ground at the same time.With what speed did he throw the second stone?

Class 9th
Physics ​

Answer 1

For first stone 

h = 49m

g = 9.8m/s²

t = ?

u = 0

apply 

h = ut + gt²/2

49 = 0 + 9.8t²/2

t² = 10

t = √10 = 3.16s

for second stone

t = 3.16 - 1 = 2.16s

h = 49m

g = 9.8m/s²

u = ?

again apply

h = ut + gt²/2

49  = u*2.16 + 9.8*2.16²/2

49 = 2.16*u + 22.86

26.14/2.16 = u

u = 12.10m/s

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Answer 2

Answer:

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