Question

11. A ball is thrown up and attains maximum height of 20 m. Calculate its initial speed. (g = 10 ms')

a) 19.7 m/s
b) 20 m/s
c) 25 m/s
d) 35m/s
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Answer 1

final velocity = 0

acceleration = - 10 m/ s 2

distance. = 20 m

u = ?

v^2 - u ^2 = 2 a s

0^2 - u^ 2 = 2 * -10 * 20

-u^2 = -400

u = √ 400

u = 20m / s