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Using the equation:

x=vot+(1/2)at2

x: -39.2m (though the object is thrown upwards, its total displacement is just the amount it fell from the tower).

vo: initial velocity

t: 4 s

a: -9.8m/s2 (assuming we're on the earth's surface)

-39.2=vo(4 s)+(1/2) (-9.8m/s2)(4 s)2

((78.4 m - 39.2 m)/ 4 s) = v0

So the initial velocity is 9.8 m/s.

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Q: An object is thrown vertically upwards from the top of a tower of height 39.2 meters reach the ground in 4 secons Find the velocity with which it is thrown upwards?
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