Pendulum period lab | Mistake Master Studio

The situation

A bob hangs from a string and swings through a small angle. Each full swing over and back takes a time called the period T. Below you will get a working pendulum with three knobs: the string length L, the bob's mass m, and the local gravitational field strength g. A photogate times 10 full swings for you.

First, commit to a prediction. Then the apparatus unlocks.

Predict first

Commit before you touch the sliders

Which changes make the period longer? Check all you expect to. Using a longer string Making the bob heavier Going to a planet with higher gravity

Plot T straight against L. What shape do you expect? A straight line (T is directly proportional to L) A curve that bends over and flattens as L grows (T is proportional to the square root of L) A flat line (length has no effect)

Explore

Test your prediction on the apparatus

Drag the sliders and time 10 swings at different settings. Or pick a test chip to lock everything but one variable and watch its relationship with T draw itself. The release angle stays small; at small angles it barely affects the period. Retiming at identical settings repeats exactly, so any change you see is real.

String length LL = 0.60 m

Bob mass mm = 1.0 kg

Gravitational field gg = 10.0 N/kg

Mystery planet: g = ?

Period vs length

Drag the unlocked slider. Every position you visit drops a measured point.

Which fit matches your points?

Measure and straighten

Which world is this?

You have landed somewhere in the solar system and the gravity readout is broken. The pendulum still works. Choose at least 5 different lengths, time 10 swings at each, divide the total by 10 to get one period T, and enter each (L, T) pair below. Then straighten the plot, and work through Read the slope: the walkthrough hands you the g of this planet only once you can say why the slope carries it.

Collect your data, then work through the Read the slope steps: they walk you to the transform that straightens the plot and the slope that carries g. Finish them and the Record button turns on and checks your g against the planet you are standing on.

Transfer

One changed variable

Back on Earth, suppose you make the string four times as long. Using the same relationship, by what factor does the period change?

T is proportional to √L. Four times the length multiplies the period by √4 = 2, so the period doubles. Notice the bob's mass never entered the reasoning, exactly as your slider showed.