Question

A stone is thrown vertically upward direction with a velocity of 20 m per second. The stone will reach the throwers hand after ?

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Answer 1

Time to reach maximum height can be obtained from v=u+at0=20+(−10)tt=2ss=ut+0.5at2=20(2)+0.5(−10)(2)2=20mThus, total distance for maximum height is 45 ms=ut+0.5at245=0+0.5(10)(t′)2t′=3sTotal time= 3+2= 5s

Answer 2

Time to reach maximum height can be obtained from v=u+at

0=20+(−10)t

t=2s

s=ut+0.5at

2

=20(2)+0.5(−10)(2)

2

=20m

Thus, total distance for maximum height is 45 m

s=ut+0.5at

2

45=0+0.5(10) ) 2t=3s

Total time= 3+2= 5s