Posted by **Morgan** on Tuesday, September 19, 2006 at 4:47pm.

A rock is thrown vertically upward with a speed of 12.0 from the roof of a building that is 40.0 above the ground. Assume free fall.

In how many seconds after being thrown does the rock strike the ground?

What is the speed of the rock just before it strikes the ground?

The position of the rock is

s = (-1/2)g*t^2 + (12m/s)*t + 40

Use the quadratic formula to find t when s = 0

The speed is |-g*t + 12| those are absolute value bars and the t from the first part.

Check my set-up for this.

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