# physics

A hoodlum throws a stone verticlly downwarsd with an inital speed of 12m/s from the roof of a building,30m above the ground

a)How long does it take the stone to reach the ground?

b)What is the speed of the stone at impact?

What would be the 2 equations for this problem?

a) Solve
Y = 30 - 12 t - (1/2) g t^2 = 0 for the elapsed time, t.
g = 9.8 m/s^2.
Take the positive root of the quadratic equation you get.
b) V (at impact) = Vinitial + g t
= -12 - 9.8 t
It will be a negative number (downwards)

1. 👍
2. 👎
3. 👁
1. 1.54 seconds
27.092 m/s

1. 👍
2. 👎

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