$$\text{Speed} = \frac{\text{distance}}{\text{time}} \qquad \text{Distance} = \text{speed}\times\text{time} \qquad \text{Time} = \frac{\text{distance}}{\text{speed}}$$ $$\text{Average speed} = \frac{\text{total distance}}{\text{total time}}$$

• Convert km/h to m/s: multiply by $\dfrac{5}{18}$. Convert m/s to km/h: multiply by $\dfrac{18}{5}$.

Relative speed

• Objects moving in opposite directions (towards each other or apart): add the speeds.
• Objects moving in the same direction: subtract the speeds. $$\text{Time to meet} = \frac{\text{distance apart}}{\text{relative speed}}$$

Acceleration

$$a = \frac{v - u}{t} \qquad \text{Deceleration (retardation)} = -a$$

Velocity-time graph

• Gradient $=$ acceleration.
• Area under the graph $=$ distance travelled.
• Average velocity $= \dfrac{\text{total displacement}}{\text{total time}}$.