Elastic Collision

Total kinetic energy of objects is conserved before and after the collision (perfectly elastic)

$$\Sigma E_{ki} = \Sigma E_{kf}$$

Derived from equation above:

$$\begin{align*} \text{RSA} &= \text{RSS} \\ \text{relative speed of approach} &= \text{relative speed of separation} \end{align*}$$

• Objects travelling in opposite directions: $v_1 + v_2$
• Objects travelling in same direction: $v_2 - v_1$

Objects move apart after collision

Solving for final velocity of two objects given mass and initial velocity

1. Write equation using principle of conservation of momentum
2. Write equation using RSA = RSS
3. Solve simultaneous equations

Inelastic Collision

Total kinetic energy of objects is not conserved before and after the collision

Objects stick together after collision