How to play Formula Test Drive
- Choose a situation and read the given values and the unknown.
- Rearrange the formula yourself, or compare the four options.
- Turn on the units check: an option whose units do not match the unknown is wrong.
- Choose a formula and press Play. The car drives with the value it gives: it should end on the line or at the target speed.
Check a rearranged formula twice
After rearranging a formula, check it in two ways. First, the units: the right-hand side must have the units of the unknown. If t = v ÷ d, the units are (m/s) ÷ m = 1/s, not seconds, so the formula is wrong. Quantities with different units can never be added. Second, the meaning: some wrong formulas have the right units, like a = (v + v₀) ÷ t, so test them on a real situation or on a simple case you already know.
A focused learning model
Each situation has constant acceleration on each part of the motion, computed exactly from the chosen value. A run that would last longer than 8 s plays faster, and the speed-up is shown. The units shown with each formula are worked out from the units of the given quantities.