PHY006 · Mechanics · Classes 9–11
Free fall
Objective: To study the motion of a freely falling object and find how distance depends on time.
🧰 Apparatus
- Steel ball
- Electromagnet release
- Light gates or video camera with a scale
- Metre scale
📐 Formulas and SI units
s = ½gt² (m)
v = gt (m/s)
t = √(2h/g) (s)
💡 Theory
In free fall every object near the Earth accelerates at g ≈ 9.8 m/s², whatever its mass (ignoring air resistance). Distance grows with the square of time: s = ½gt², so in equal time intervals the distances fallen are in the ratio 1 : 3 : 5 : 7.
🪜 Procedure
- Release the ball from rest beside a vertical scale.
- Record the fall with a video at a known frame rate (or use light gates).
- Read the position at equal time intervals.
- Plot s against t² and find the slope (= g/2).
- Repeat with a different ball mass.
📋 Observations Simulated values
✅ Result and conclusion
A 20 m drop takes 2.02 s and lands at 19.8 m/s; heavy and light balls fall together.
🔬 In a real lab
Air resistance slows light or large objects (a feather falls slowly); in a vacuum tube all objects fall together.
⚠️ Safety
Drop only small balls into a sand tray; never drop objects from height where people walk.
❓ Quick check
1. A heavy and a light ball dropped together (no air)…
2. Distance fallen in the first second?
3. Speed after 3 s of free fall?
🏋️ Practice
EasyTime to fall 45 m?
Answer: ≈ 3.03 s
MediumDistances in successive seconds are in the ratio…?
Answer: 1 : 3 : 5 : 7
ChallengeA stone falls for 2 s. Distance?
Answer: 19.6 m