Kinematics of motion in a straight line

Need to know

What you need to know

• $v = u + at$
• $s = ut + \frac{1}{2}at^2$
• $s = vt - \frac{1}{2}at^2$
• $s = \frac{1}{2}(u+v)t$
• $v^2 = u^2 + 2as$

Explanation

The Language of Motion

1. SUVAT for constant acceleration — pick the equation that doesn't involve the variable you don't need.
2. The gradient of a displacement-time graph is velocity. The gradient of a velocity-time graph is acceleration.
3. For objects in free fall, acceleration 'a' is the acceleration due to gravity, 'g' (approx 9.8 m s⁻²). Remember to define a positive direction and stick to it.
4. When acceleration changes, use calculus: differentiate displacement to get velocity (v = ds/dt), and differentiate velocity to get acceleration (a = dv/dt).