Posted by **Abbey** on Friday, April 16, 2010 at 3:07pm.

Projectile motion: Let's suppose you throw a ball straight up with an initial speed of 50 feet per second from a height of feet.

a) Find the equation that describes the motion as a function of time.

My answer was x = 0 and y=-16t^2+50t+6

b) How long is the ball in the air?

This is the part I need help on. Can I put the y equation into my graphing calculator to solve for t?

- Math -
**bobpursley**, Friday, April 16, 2010 at 3:13pm
you can, but it is not necessary.

when it returns to ground, y=0

0=-16t^2+50t+6

16t^2-50t-6=0

using the quadratic equation...

t= (50+-sqrt(2500+384)/32

t=(50+-sqrt 53.7)/32=103.7/32=3.24sec

Your graphing calc may have a subrouting to solve quadratic equations, many do.

check my work.

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