For motion in a straight line with constant acceleration, five quantities are linked: s (displacement), u (initial velocity), v (final velocity), a (acceleration) and t (time). These are the SUVAT equations: v = u + at, s = ut + ½at², s = ½(u + v)t, v² = u² + 2as and s = vt − ½at².
List the three values you know and the one you want, then pick the equation that contains exactly those four. Take care with direction: choose one direction as positive and give the others a minus sign.
Worked example
u = 9 m/s, v = 25 m/s and a = 2 m/s². Find t.
- Use v = u + at: 25 = 9 + 2t.
- 2t = 16.
Answer:t = 8 s
Key words
- displacement (s)
- distance in a given direction
- velocity
- speed in a given direction
- acceleration
- rate of change of velocity
Practise this
New questions every time.