# Calculating Time in gravity/acceleration problem

1. ### jquiring

1
I understand that gravity acts upon objects at a fairly steady rate on earth. How could I calculate the time in the following example:

An object falls ten centimeters before hitting the ground. How much time has passed from when it fell to when it hit the ground?

I can't use a stopwatch because the distances are so small. Since gravity is a constant (9.8 m/s2), how can I calculate the time over such a short distance? I'm sure that a computer could calculate this almost instantly, but I would like to know how to perform the calculation on paper.

2. ### mathman

6,658
The general form for your problem is d=vt+gt2/2, where v is the initial speed and d is the distance. Air resistance is neglected. Assuming you simply drop it, you will get t=(0.2/9.8 )1/2 sec.

Last edited: Apr 9, 2008
3. ### Awsom Guy

77
Not d, it is s for displacement :).