Question

find the initally velocity of an object projected vertically upward if it take 20 sec to reach maximum height
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Answer 1

for upward motion

acceleration = - g

at maximum height v = 0

now

v = u + at

0 = u -g 20

u = 20g m/s

(g = acceleration due to gravity)

if we take g = 9.8 mps^2

u = 20*9.8

= 196 mps