Kinematics and SUVAT Equations

Apply the SUVAT equations for constant acceleration at A-Level. Solve problems with displacement, velocity, and time.

The SUVAT equations describe motion with constant acceleration. They connect displacement (ss), initial velocity (uu), final velocity (vv), acceleration (aa), and time (tt).

The SUVAT Equations

  1. v=u+atv = u + at
  2. s=ut+12at2s = ut + \frac{1}{2}at^2
  3. s=(u+v)t2s = \frac{(u+v)t}{2}
  4. v2=u2+2asv^2 = u^2 + 2as
  5. s=vt12at2s = vt - \frac{1}{2}at^2

Strategy

  1. List known quantities (s,u,v,a,ts, u, v, a, t).
  2. Identify the unknown.
  3. Choose the equation that uses the three knowns and the unknown.

Worked Example: Example 1

Problem

u=5u = 5 m/s, a=2a = 2 m/s², t=4t = 4 s. Find ss.

s=5(4)+12(2)(16)=20+16=36s = 5(4) + \frac{1}{2}(2)(16) = 20 + 16 = 36 m.

Solution

Worked Example: Example 2

Problem

u=20u = 20 m/s, v=0v = 0 (stops), a=4a = -4 m/s². Find ss.

0=400+2(4)s0 = 400 + 2(-4)ss=50s = 50 m.

Solution

Worked Example: Vertical Motion

Problem

Ball thrown up at 15 m/s. g=9.8g = 9.8 m/s². Max height: v=0v = 0.

0=2252(9.8)s0 = 225 - 2(9.8)ss=11.5s = 11.5 m.

Solution

Practice Problems

    1. u=0u = 0, a=3a = 3, t=6t = 6. Find vv and ss.
    1. A car brakes from 30 m/s to rest in 5 s. Find deceleration and distance.
    1. Stone dropped from 80 m. How long to hit the ground?

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Key Takeaways

  • 5 SUVAT equations for constant acceleration.

  • List knowns → choose the right equation.

  • Use g=9.8g = 9.8 m/s² for gravity (take positive direction consistently).

  • These only work for constant acceleration.

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