Posted by **Keith** on Tuesday, January 25, 2011 at 4:21pm.

a girl throws a ball vertically upwards at 5m/s from the roof of a building 20m high

how long will it take the ball to reach the ground? and what will its speed be when it strikes the ground

- physics -
**bobpursley**, Tuesday, January 25, 2011 at 4:27pm
when at the top, vertical velocity is zero

vf=0=vi+gt solve for t, time to top.

How long it will take to get to the ground?

Hf=Hi+vi*t-1/2 g t^2 hi=20, hf=0, solve for t to get time in the air.

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