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## Homework Statement

A stone is thrown off a cliff upward at a rate of 10 m/s. It then falls from the height of the throw down into a lake 20M below. How long does it take for the stone to fall? What is its impact velocity? What is the height of the cliff?

## Homework Equations

v=vi+at

x=xi+vi+1/2at^2

## The Attempt at a Solution

x=xi+vi+1/2at^2

20=0+0+1/2(9.8 x t^2)

40=9.8t^2

t^2=4

t=2.02s

v=vi+at

v=0+(9.8)(2.02)

v=19.8 m/s

x=final distance

xi=initial distance

vi=initial velocity

v=final velocity

a=acceleration of gravity (9.8)

t=time

Can someone help me to find the height of the cliff? I got the time and impact velocity but am unsure of how to get the heigh of the cliff. Thanks! :)