Calculating Time in gravity/acceleration problem

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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.
 

Answers and Replies

mathman
Science Advisor
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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.
 
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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.
Not d, it is s for displacement :).
 
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