Expert: Abe Mantell - 1/6/2012

Question
I've got a test for quadratics in a few days, and I don't understand the homework we are doing still.
Can you please explain how to do these problems? My teacher gives lectures during class but I still don't understand what she means.
For example:
according to legend, in 1589, the Italian scientist Galileo Galilei dropped two rocks of different weights from the top of the Leaning Tower of Pisa. He wanted to show that the rocks would hit the ground at the same time. Given that the tower's height is about 177 feet, how long would it have taken for the rocks to hit the ground?

Answer
Hello John,

The equation governing the motion of an object subject to acceleration is:
y(t)=(1/2)at^2+vot+yo, where a=the acceleration, vo=initial velocity, yo=initial position

In this case: a=g=-32.17 ft/sec^2, vo=0 (since the rocks are dropped not thrown)
and y0=177 ft, y(t)=0 (hitting the ground)

==> 0=(1/2)(-32.17)t^2+177 ==> t^2=11.004 ==> t=3.32 seconds

I hope this helps.

Abe