Question

A ball is thrown vertical upward at the reaches at height of 90 m find the velocity with which it was thrown


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Answer 1

Given the height achieved by the ball h=Displacement of the ball= 90m
The final velocity of the ball v is 0.
Let the initial velocity by which the ball was thrown be u.
Acceleration of the ball= -g = -9.8m/sec^2
Using the third law of moton we get,
v^2-u^2=2as
or, v^2-u^2 = -2gh
or, 0^2 - u^2 = -2×9.8×90
or, 0 - u^2 = -1764
or, u^2 = 1764
or, u=√1764
or, u=42 m/sec
Therefore the initial velocity by which the ball was thrown was 42 m/sec.