Measuring g with a Simple Pendulum: Virtual Required Practical
A virtual simple pendulum practical: measure l and d, choose the length to use, the release angle, where to start the stopwatch and how many oscillations to time, by hand or automatically. Plot T² against L, take g from the gradient, read the intercept, and find out why forgetting the bob's radius leaves the gradient unchanged.
About this simulation
- What
- An interactive Physics simulation of Measuring g with a Simple Pendulum: Virtual Required Practical.
- Who
- Designed for AP, IB, and A‑Level Physics students.
- How
- Runs in any modern browser — drag, adjust, and explore in real time.
Updated 2026-10-11
Key Concepts
Period of a simple pendulum
For small angles T = 2π√(L/g), independent of the mass and the amplitude. L is measured to the centre of the bob.
Random and systematic error
Reaction time scatters each timing (random); forgetting the radius or miscounting shifts every result the same way (systematic).
Reducing uncertainty
Time many oscillations and start at the equilibrium position: the reaction error is shared over n periods.
Linearising: T² against L
T² = (4π²/g)L is a straight line through the origin; g = 4π²/gradient, and a constant length error only moves the intercept.
What This Simple Pendulum Lab Teaches
Measuring g with a simple pendulum is the classic practical for measurement skills: it is part of AQA A-level required practical 7, a standard AP Physics 1 lab and the pendulum experiment in the Chinese textbook. The physics is one formula; the marks are in the method — what L is, where to start the stopwatch, how many oscillations to time and what to plot.
Here every one of those decisions is yours. The metre rule has 1 mm resolution, the stopwatch is pressed with a realistic reaction error, and in manual mode it is your own reaction time. Record timings at several lengths, plot T² against L and take g from the gradient.
The analysis compares the gradient value with the mean of single-run values, shows where the line crosses the L axis and lists the systematic and random errors in your data, so you can see why the graph method survives a forgotten radius.
