Required Practical 7: Reaction Time

Method (Ruler Drop Test)

1. Person 1 sits on a stool with good posture, dominant arm on table, hand overhanging edge.

2. Person 2 holds ruler vertically, 0 cm mark between Person 1’s thumb and finger.

3. Person 2 tells Person 1 to get ready → drops ruler at a random time.

4. Person 1 catches ruler as quickly as possible with thumb and finger.

5. Person 2 records measurement at top of Person 1’s thumb.

6. Person 1 rests → repeat several times → calculate mean distance.

7. Convert distance to reaction time using a conversion table.

8. Swap roles → test both people.

Variables

• Independent variable = person being tested (or factor you choose to change, e.g. practice, hand used, caffeine).

• Dependent variable = reaction time.

• Control variables:

  • Starting distance between thumb & finger.

  • Always measure ruler at top of thumb.

  • Same room conditions (lighting, noise, distractions).

Possible Extensions

• Effect of practice → repeated trials may reduce reaction time.

• Dominant vs non-dominant hand → dominant hand usually faster.

• Effect of chemicals (e.g. caffeine) → test with cola vs caffeine-free cola.

Safety Considerations

• Check participant has no medical issues (e.g. allergy, heart condition) before giving caffeine.

• Carry out in a safe lab environment (no hazardous chemicals nearby).

✅ Key takeaway: This is a required practical. Learn the method, variables, and safety precautions as exam questions often ask you to design, improve, or evaluate this experiment.