Reaction time of dollar falling between fingers

[alexs2jennisha]

Homework Statement

If you are worried about safely driving after a party, I recommend you just not drive! But if you want to
see when you are finally okay to drive, here is a test to see if you are still too “impaired”. Take a dollar bill
and have a friend hold the bill from one of the short sides hanging straight down. Place your thumb and
forefinger opposite the bottom of the bill. Have your friend release the paper suddenly and try to catch it
with your thumb and forefinger. If you can catch this bill three times in a row, you are not too badly
impaired. Assuming the bill was falling freely without air resistance (not a bad assumption for the paper
falling sideways), calculate your reaction time. That is, how long does it take for the entire length of the
bill to fall between your fingers? (Use your hand to measure a dollar bill based on your body
measurements.)

i know that the acceleration is -9.8m/s²

Homework Equations

I was thinking of using d = v_it + 1/2at²

but i don't know d

The Attempt at a Solution

if i do know d am i choosing the right equation?

 

[ehild]

How is d related to the size of the dollar bill? (You can find the sizes here : http://en.wikipedia.org/wiki/United_States_one-dollar_bill

You showed the correct equation.

ehild