Experiment 2 — How Fast Is the Trolley?

Topic: Physics · Classes 6–7 · Motion and time: speed = distance ÷ time

Aim: Measure the trolley’s speed to within 5% of its true value (0.60 m/s).

Daily: A speed camera, a train timetable and a runner’s stopwatch all use distance ÷ time. Knowing how to reduce measuring error is what separates a rough guess from a real measurement.

Question: The same stopwatch error of 0.3 s is made over 1 m and over 5 m. Which measurement is more accurate?

Exp: Over a longer run the total time is bigger, so a fixed error forms a much smaller fraction of it.

Exp: Speed tells how much distance is covered per unit of time.

Question: A trolley covers 6 m in 12 s. Its speed is…

Question: To convert 10 m/s into km/h, multiply by…

Question: Averaging three trials mainly reduces…

Exp: Random errors partly cancel when averaged.