Posted by **Joe** on Tuesday, January 8, 2013 at 8:37am.

A rock is thrown upwards (vertically) from the ground with an initial velocity of 40 feet per second. If acceleration due to gravity is -10 feet per second squared, how high will the rock go?

- Calc -
**Reiny**, Tuesday, January 8, 2013 at 9:03am
You are using the wrong units, the value of -10 is associated with metres not feet. (actually in most cases it is considered -9.8 )

I will assume you meant metres, not feet

height = -5t^2 + 40t

velocity = -10t + 40

at max height, velocity = 0

-10t+40 = 0

t= 4

height = -5(4^2) + 40(4) = 40 m

If your problem stated feet, then the equation would have been

height = -16t^2 + 40t

etc

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