Key Concepts: Equations of Motion (Constant Acceleration)

The Kinematic Equations (SUVAT)

These equations apply when acceleration a is constant. The five variables are: s (displacement), u (initial velocity), v (final velocity), a (acceleration), t (time).

• v = u + at — final velocity from initial velocity and acceleration.
• s = ut + ½at² — displacement from initial velocity, acceleration, and time.
• v² = u² + 2as — relates velocities to displacement (no time needed).
• s = ½(u + v)t — displacement from average velocity.

Using the Equations

• Identify what you know (3 of 5 variables) and what you want to find.
• Choose the equation that contains your known variables and the unknown.
• Be consistent with signs: pick a positive direction and stick with it.

Important Notes

• These equations assume constant acceleration — they fail if acceleration changes.
• For free fall, use a = g = 9.8 m/s² (downward).