# Falling object problem. ..

• Sep 13th 2009, 09:45 PM
Godzilla
Falling object problem. ..
suppose an object is dropped from a height of x above the ground. Then its height after t seconds is given by h=-16tē+x, where h is measured in feet. Use this info to solve the problem.

A ball is dropped from the top of a building 96 ft tall.

How long will it take to fall half the distance to ground level??

How do you solve this? Thanks.
• Sep 13th 2009, 09:54 PM
VonNemo19
Quote:

Originally Posted by Godzilla
suppose an object is dropped from a height of x above the ground. Then its height after t seconds is given by h=-16tē+x, where h is measured in feet. Use this info to solve the problem.

A ball is dropped from the top of a building 96 ft tall.

How long will it take to fall half the distance to ground level??

How do you solve this? Thanks.

Well, you are given that x=96feet.

so put that in

$\displaystyle h=-16t^2+96$

and this gives the height after t seconds.

now you want to find t when the thing is half its initial hieght, so

$\displaystyle \frac{1}{2}96=h=-16t^2+96$

solve for t

I just edited my post, I copied and pasted alot from yours and assumed tha it would remain the same (the t did not stay squared). Sorry if there was any confusion.
• Sep 14th 2009, 07:33 AM
fluke
$\displaystyle h = -16t^2 + x$

At time , t = 0 h = 96 ft $\displaystyle 96 = - 16(0)^2 + x$

therefore , x = 96

we get this equation $\displaystyle h = -16t^2 + 96$

$\displaystyle h = 0.5(96) = 48$ sub into the equation

$\displaystyle 48 = -16t^2 + 96$

$\displaystyle -48 = -16t^2$

$\displaystyle t ^ 2 = 3$

$\displaystyle t = \sqrt{3}$