Brainlag Plusv² − u² = 2as for braking distances and falling objects, and the SUVAT solver for checking your working.
Five letters, one equation
When the acceleration is constant, five quantities describe the motion: s (displacement), u (initial velocity), v (final velocity), a (acceleration) and t (time).
GCSE gives you this one on the equation sheet:
v² − u² = 2 a s
It has no t in it, so use it when the question does not mention time.
- A car at 20 m/s brakes at 5 m/s² to a stop. Braking distance?
- u = 20, v = 0, a = −5 (slowing, so negative)
- 0 − 20² = 2 × (−5) × s
- −400 = −10 s, so s = 40 m
Write down the three letters you know and the one you want before you touch the numbers. Most mistakes are a wrong sign on a.
The rest of this lesson and its 8 practice questions are in Plus.
Screen 1 of 4, free to read.
- 8 exam-style questions, marked as you go, each with a worked solution
- The SUVAT Solver</b> and the <b>Projectile motion simulation beside every question
- Anything you get wrong is saved to your flashcards