What is reaction of time?

Age: 6+ Time: 15 minutes

What you need:

What to do:

1. Sit in a chair and rest your arm on a table so that your wrist hangs off the edge and your hand is sideways (thumb side facing up). Ask the other person to hold end of the ruler (where the numbers finish), pinching just the very top, and hold the ruler over your hand so the bottom (where the numbers start) dangles just above your hand.

2. Tell your partner to release the ruler at a random time, with no countdown or warning. Using your thumb and index finger, try to catch the ruler as quickly as possible. Once you’ve caught it, keep holding it, leaving your finger and thumb in the same place on the ruler.

3. Notice the measurement on the ruler where your thumb and finger landed (5 cm, 7 cm, etc.) Write down the number on your piece of paper and compare it to the chart below. What is your reaction time?

4. Repeat the experiment again and compare the results. What is your reaction time after three tries? What about after 8 or 10 tries?

5. Switch places with your partner and let them try it.

6. Questions to think about:

What’s happening?

Your reaction time is the amount of time it takes for your brain to process and respond to something it senses. As your partner releases the ruler, light bounces off it and enters your eye, giving visual information about the movement. Your brain receives the information, processes it, and determines how to react. Your brain will then send a signal to your fingers telling them to close. While each of these things happens very fast, together they add up to a visible delay between when the ruler starts to move and when you catch it. The chart in this activity uses the distance the ruler traveled (the centimeter measurement where your finger landed) to calculate how much time passed before your fingers closed.