Measuring Reaction Time
An activity from the Burroughs Wellcome Student Research Program The Science of Sports

Problem:

One carnival game places a one hundred dollar bill vertically between your index finger and thumb so that one half of the bill is below your hand and half is above. If you can catch the bill with that finger and thumb you can keep it. Is it possible to win this game?

Introduction:

A person's reaction time is a measure of how quickly they can respond to a given stimulus. How long it takes to react to a rebound could mean the difference between a win and a loss. How long it takes to react to a stopped vehicle can mean the difference between a safe stop and a collision. It is important to know your limitations before it becomes a life and death situation.

Since an average human reaction time is only a fraction of a second, it would be impossible to measure it directly. By using the known properties of gravity, we can determine how long it takes a person to respond to the dropping of an object by measuring how far the object can fall before it is caught.

Materials
meter stick calculator

Procedure:

For this activity you must work with a partner. Have your partner rest their elbow near the edge of a table so that their wrist can extend over the side. Hold the meterstick vertically in the air between (but not touching!) your partner's thumb and index finger. Note the position on the meterstick below your partner's thumb or finger. Instruct your partner to catch the meterstick as quickly as possible as soon as they see it fall. WITHOUT warning, drop the meterstick. Record, in meters, the distance the meterstick fell. Repeat 9 times for ten trials.

Trade places with your partner and repeat the experiment.

Find the average distance the meterstick fell. The following formula relates the time an object falls to the distance the object fell from rest:
d = (1/2) g t²
d = the distance the object fell
g = the acceleration of gravity
t = the time the object was falling

Use this equation to determine the average reaction time for you and your partner.

If you have extra time after doing the calculations and addressing the discussion and conclusion sections repeat the experiment, but this time have the person catching the meterstick sing (or hum) their favorite song while trying to catch it.

Data Table

.

Trial	Your Distance (m)	Partner's Distance (m)	Reaction Time
1	.	.	.
2	.	.	.
3	.	.	.
4	.	.	.
5	.	.	.
6	.	.	.
7	.	.	.
8	.	.	.
9	.	.	.
10	.	.	.
Average	.	.	.

Discussion:

• You probably did not get the exact same reaction time for each of your ten trials. What factors might keep you from reacting the same each trial?
  
  
• If you wanted to know how long it might take you to react to any given stimuli, would it be better to consider your fastest, slowest, or average reaction time? Why?
  
  
• List at least 3 factors that might affect reaction time. That is, what might make one person have a faster or slower reaction time then another person.
  
  
• Consider the entire class data.
  • What was the longest reaction time?
  • What was the shortest reaction time?
  • What was the most consistent reaction time?
  • What is average reaction time for the girls?
  • For the boys?
  • Do you believe that gender is a factor that affects reaction time? Explain.
  
  
• Name as many specific sports examples that you can think of that are highly dependent on a person's reaction time.

Conclusion
Write a short paragraph that answers the problem question.