CAMBRIDGE IGCSE PHYSICS (0625)

Simple Pendulum Master Guide

Interactive Lab Simulator & Exam Practice Questions

🧪 1. Mobile Physics Simulator

CALCULATED PERIOD (T) 2.01 s

Lab Adjustments

12°
(Adjusting slider resets start position)
1.00 m
0.50 kg

📌 2. Why Pendulums Matter in Physics

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Measuring Gravity

Determines local gravitational acceleration (g ≈ 9.81 m/s²) with a simple ruler and stopwatch.

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Mass Independence

Proves gravitational mass equals inertial mass. Changing bob mass does not alter period T!

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Harmonic Motion

Demonstrates Simple Harmonic Motion (SHM) where restoring force is proportional to displacement.

📐 3. Formula & Mass Cancellation Proof

The time required for 1 complete cycle (Period, T) is:

T = 2π × √(L / g)
  • T (Period): Time in seconds for one back-and-forth swing.
  • L (Length): Length from clamp to center of mass (m).
  • g (Gravity): Acceleration due to gravity (9.81 m/s²).

Proof: Why Mass Doesn't Matter

1. Restoring Force: F = m × g × sin(θ)
2. Newton's 2nd Law: F = m × a
3. Set Equal: m × a = m × g × sin(θ)
4. Cancel Mass m: a = g × sin(θ)

A heavier mass experiences a larger gravitational force, but its greater inertia resists acceleration by the exact same proportion!

📋 4. Cambridge IGCSE Experimental Rules

STEP 1: MEASURE L

Measure string length from bottom of wooden clamp blocks to center of the bob.

STEP 2: TIME 20 SWINGS

Record time for 20 complete oscillations (t) to reduce percentage human reaction error.

STEP 3: FIDUCIAL MARKER

Place a marker at the center line (equilibrium) where the bob travels fastest.

📊 5. Experimental Data & g Calculator

Length L (m) Time for 20 Swings t (s) Period T = t/20 (s) T² (s²) Calculated g (m/s²)
AVERAGE EXPERIMENTAL GRAVITY (g) 9.81 m/s²

📝 6. IGCSE Exam-Style Practice Questions

Authentic Paper 4 & Paper 6 exam questions with hidden mark-scheme solutions.

PAPER 6 PRACTICAL • 3 MARKS

Q1. A student measures the period T of a pendulum for length L = 0.80 m. She records the time for 20 oscillations as t = 36.0 s.

(a) Calculate the period T and T².
(b) Explain why timing 20 oscillations gives a more accurate value for T than timing 1 oscillation.

Mark Scheme Answer:
(a) Period T = 36.0 / 20 = 1.80 s.
T² = (1.80)² = 3.24 s².
(b) Timing 20 oscillations reduces the impact of human reaction time error on the final period calculation (divides reaction error by 20).
PAPER 4 THEORY • 2 MARKS

Q2. A student plots a graph of T² (y-axis) against L (x-axis) and obtains a straight line passing through the origin with gradient G = 4.02 s²/m.

Given that T² = (4π² / g) × L, calculate the acceleration due to gravity g.

Mark Scheme Answer:
Gradient G = 4π² / g
g = 4π² / G = (4 × 3.1416²) / 4.02 = 39.478 / 4.02 = 9.82 m/s².
PAPER 6 PRACTICAL • 2 MARKS

Q3. State two experimental precautions needed to ensure accurate results when measuring length L and timing oscillations.

Mark Scheme Answer (Any 2):
1. View rule at eye-level to avoid parallax error when measuring length L.
2. Measure length L to the center of the sphere/bob (center of mass).
3. Use a fiducial marker placed at the center (equilibrium position) to count swings.
4. Ensure initial release angle is small (< 15°).