Calculating Time in gravity/acceleration problem

jquiring

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.

mathman

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.

Awsom Guy

Not d, it is s for displacement :).