Ball At Max Height

magentarita · #1 $Old$ 11-18-2008, 12:23 AM

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?

Soroban · #2 $Old$ 11-18-2008, 01:24 PM

Hello, magentarita!

Quote:

Vanessa throws a tennis ball in the air.
The function $h(t) \:=\:–16 t^2+ 45t+ 7$ 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?

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

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

The ball is at maximum height in about 1.4 seconds.

magentarita · #3 $Old$ 11-18-2008, 11:35 PM

Quote:

Originally Posted by Soroban $View Post$

Hello, magentarita!

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

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

The ball is at maximum height in about 1.4 seconds.

I hope that you can help me with questions privately.