Mathematics ยท WME01 (M1)

Constant acceleration (suvat)

When acceleration is constant, five quantities are linked by five equations.

The letters

s = displacement (m), u = initial velocity (m/s), v = final velocity (m/s), a = acceleration (m/s2), t = time (s).

The equations

Pick the one that leaves out the quantity you neither know nor want.

Signs

Choose a positive direction and stick to it. For vertical motion under gravity, use g = 9.8 m/s2 (the value Pearson uses unless told otherwise), with the sign set by your positive direction.

Worked example

A car accelerates from 4 m/s at 2 m/s2 for 5 s. How far does it travel?

  1. u = 4, a = 2, t = 5, want s.
  2. s = ut + (1/2)at2 = 20 + 25

Answer: s = 45 m

Key idea: List s, u, v, a, t; choose the equation without the unwanted letter; keep one positive direction.

Check yourself

  1. u = 3 m/s, a = 2 m/s2, t = 4 s. Find v.
    Show answer

    11 m/s. v = u + at = 3 + 8 = 11 m/s.

  2. A particle starts from rest and accelerates at 4 m/s2 for 3 s. Find s.
    Show answer

    18 m. s = ut + (1/2)at2 = 0 + 18 = 18 m.

  3. u = 6 m/s, a = 2 m/s2, s = 7 m. Find v.
    Show answer

    8 m/s. v2 = 36 + 28 = 64, so v = 8 m/s.

  4. A car slows from 20 m/s to rest in 5 s. Find its acceleration.
    Show answer

    -4 m/s2. a = (v - u)/t = (0 - 20)/5 = -4 m/s2 (a deceleration of 4).

  5. You know u, a and t and want s. Which equation do you use?
    • v2 = u2 + 2as
    • v = u + at
    • s = ut + (1/2)at2
    • s = vt - (1/2)at2
    Show answer

    s = ut + (1/2)at2. It contains s, u, a and t and leaves out v.

Practise with instant feedback

Sources

Last updated 7 November 2026. Spotted a mistake? Email alevel@lifereadysociety.com.