Learners investigate how pendulum length affects period. Which procedure best supports a fair inquiry?

Correct answer: Vary length, control other conditions and repeat trials. A fair test varies one factor (length), controls other conditions, and repeats trials to improve reliability.

• Change both length and mass during each trial. Changing both length and mass confounds the result.
• Conduct one trial for each selected length. One trial per length gives unreliable results.
• Change the release angle with every new length. Changing the release angle with each length also confounds the result.