Math Is Fun Forum

westjadew

Guest

Quadratic equations

Hello,
I need help with this exercise.

A ball is launched upward at a speed of 20 meters per second (m/s) from a 60-meter tall platform.  The equation for the ball’s height (h in meters) at time t seconds after launch is h = -4.9t2 + 20t + 60.   How long before the ball hits the ground?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: Quadratic equations

hi westjadew

Welcome to the forum.

When the ball hits the ground h = 0

So put that value into the quadratic equation and try to find it's two factors.  One will be negative so you can disregard that.  The other is the answer you want.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob