Fast Money Activity
A fun game to play with your friends is to see if they
can catch money (such as a dollar bill) when you drop
it before it falls through their hand. The ability to
catch the bill will depend on their eye-to-hand
reaction time (the length of time it takes for them to
close their hand once they see the bill starting to fall.
The easiest most accurate way to measure this time
not to measure the time but to measure the falling
distance of a ruler before you can catch it.
Determining Reaction Times by measuring distance:
1.) Hold a ruler near your partner’s hand as illustrated (above right) –> 0 cm on the ruler should be even with
the top of your partner’s hand.
2.) Make sure the ruler will fall freely through your partner’s hand and wiggle the ruler a little so that your
partner cannot anticipate the ruler’s drop.
3.) When you are both ready – release the ruler to let it fall. Your partner should attempt to catch it as quickly
as they can.
4.) The ruler will free fall through your partner’s hand and when it is caught –> the top of your partner’s hand
will be level with the distance on the ruler that it fell.
5.) Write down the distance the ruler fell in a table (in meters, i.e. 15cm = .15m) and repeat the experiment 4
more time (total = 5 trials). Cross-out your highest and lowest values (which may be quite extreme) and
average your middle three falling distances.
Falling
1
distances
2
(in meters)
3
4
5
Average
of middle 3
Now calculate your eye-to-hand reaction time:
1 2
2d
to solve for time.
at to the form t =
a
2
Use acceleration = 10m/s2 and remember put your average distance in meters.
Here is a sample calculation for a falling distance of 15cm:
2d
2(.15m)
!= .173s reaction time =!(about 1/5sec)
=
t =
a
10m / s 2
• You will need to rearrange the equation: d =
Show your reaction time calculation here:
!
!
All U.S. currency bills are 15.5cm in length – which means playing this game with 1 $US bills - someone would
have catch the bill in ½ that length (7.75cm, see drawing at top). Below, calculate the reaction time of a person who
could consistently catch a bill before it falls 7.75cm. Would anyone in your class make $money at this game
considering their calculated reaction times?