Catch a Falling Dollar

This experiment demonstrates human reaction time using a dollar bill. A person tries to catch the bill as it falls, but usually fails because the human reaction time is slower than the time it takes the bill to drop through their fingers.

1. Hold a dollar bill by its top edge so that it hangs vertically.
2. Ask a volunteer to place their thumb and forefinger around the bottom edge of the bill, ready to catch it without touching.
3. Without warning, release the bill and challenge them to catch it before it slips through their fingers.
4. Observe that most people fail because the bill falls too quickly for their reaction time.
5. Demonstrate catching it yourself by releasing and grabbing at the same time, explaining that this is not true reaction time but pre-planned movement.

Dollar Bill Drop | Introduction to Psychology - The University of Georgia Online Learning:

📄 Catch A Falling Dollar - Indiana Public Media: https://www.ipm.org/show/amomentofscience/2020-01-07/catch-a-falling-dollar

• Try different denominations of bills (or slips of paper) and jokingly suggest the value might improve reaction speed.
• Measure actual reaction time by recording the distance the bill falls before being caught.
• Compare the reaction times of different participants and calculate averages.

• Keep the demonstration lighthearted to avoid frustration.

• Why is the demonstrator able to catch the bill while the volunteer usually fails? (Because the demonstrator controls both the release and the catch, bypassing reaction delay.)
• How long does it take for signals to travel from the eyes to the brain to the hand? (About 0.2 seconds or more, which is longer than the bill takes to fall its own length.)
• How could you design a fair test to measure actual reaction time? (Mark the bill with measurements and record where it is caught.)
• Would the result change if you used a heavier bill or different object? (The principle is the same—mass doesn’t affect free-fall speed under gravity in this short distance.)