# Ball At Max Height

• Nov 17th 2008, 10:23 PM
magentarita
Ball At Max Height
Vanessa throws a tennis ball in the air.
The function h(
t) = –16t^2 + 45t + 7 represents the distance, in feet, that the ball is from the ground at any
time
t. At what time, to the nearest tenth of a second, is the ball at its maximum height?

• Nov 18th 2008, 11:24 AM
Soroban
Hello, magentarita!

Quote:

Vanessa throws a tennis ball in the air.
The function $\displaystyle h(t) \:=\:–16 t^2+ 45t+ 7$ represents the distance, in feet,
that the ball is from the ground at any time $\displaystyle t$.
At what time, to the nearest tenth of a second, is the ball at its maximum height?

The graph is a down-opening parabola. .Its maximum is at its vertex.

The vertex is: .$\displaystyle t \:=\:\frac{\text{-}b}{2a} \:=\:\frac{\text{-}45}{2(\text{-}16)} \:=\:\frac{45}{32}\:=\:1.40625$

The ball is at maximum height in about 1.4 seconds.

• Nov 18th 2008, 09:35 PM
magentarita
great work...........
Quote:

Originally Posted by Soroban
Hello, magentarita!

The graph is a down-opening parabola. .Its maximum is at its vertex.

The vertex is: .$\displaystyle t \:=\:\frac{\text{-}b}{2a} \:=\:\frac{\text{-}45}{2(\text{-}16)} \:=\:\frac{45}{32}\:=\:1.40625$

The ball is at maximum height in about 1.4 seconds.

I hope that you can help me with questions privately.