Expert: Sherman D. - 12/19/2005

Question
Suppose a ball is dropped from a window 35 meters above the ground.
 a.  Find the height of the ball after 1 second.
 b. When will the ball hit the ground?  

Answer
s(t) = (1/2)at^2 + VoT + So

In this case

a = -9.8
So = 35
VoT = 0

s(t) = (1/2)(-9.8)t^2 + 35
s(t) = -4.9t^2 + 35
s(t) = -(4.9t^2 - 35)

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a.)
s(1) = -(4.9(1)^2 - 35)
s(1) = -(4.9 - 35)
s(1) = -(-30.1)
s(1) = 30.1 meters

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b.)
0 = -(4.9t^2 - 35)
4.9t^2 - 35 = 0
4.9t^2 = 35
t^2 = (35/4.9)
t^2 = (350/49)
t = about 2.67 seconds

If you go to www.mcasco.com/p1consta.html and look near the bottom of the page with the pencil on top of a bubble sheet. To the left of that is the explaination.

the original formula is x - x0 = VoT + (1/2)at^2, which turns in x = (1/2)at^2 + VoT + x0

To make sure this is right, i will ask someone else to see what they have to say.