### Elastic Collision

Elastic collision is the collision where the kinetic energy is conserved after the collision.

Total Kinetic Energy before Collision

= Total Kinetic Energy after Collision

Additional notes:

- In an elastic collision, the 2 objects separated right after the collision, and
- the momentum is conserved after the collision.
- Total energy is conserved after the collision.

### Inelastic Collision

Inelastic collision is the collision where the kinetic energy is not conserved after the collision.

Additional notes:

- In a perfectly elastic collision, the 2 objects attach together after the collision, and
- the momentum is also conserved after the collision.
- Total energy is conserved after the collision.

**Example - Perfectly Inelastic Collision**:

A lorry of mass 8000kg is moving with a velocity of 30 ms

^{-1}. The lorry is then accidentally collides with a car of mass 1500kg moving in the same direction with a velocity of 20 ms

^{-1}. After the collision, both the vehicles attach together and move with a speed of velocity v. Find the value of v.

**Answer**:

(IMPORTANT: When 2 object attach together, they move with same speed.)

m

_{1}= 8000kg

m

_{2}= 1500kg

u

_{1}= 30 ms

^{-1}

u

_{2}= 20 ms

^{-1}

v

_{1}= v

v

_{2}= v

According to the principle of conservation of momentum,

m

_{1}u

_{1}+ m

_{2}u

_{2}= m

_{1}v

_{1}+ m

_{2}v

_{2}

(8,000)(30) + (1,500)(20) = (8,000)v+ (1,500)v

270,000 = 9500v

v = 28.42 ms

^{-1}

External Link

HyperPhysics - Elastic and Inelastic Collision

Types of Collision

Interactive Animation

Elastic and Inelastic Collision 1 - Java Applet

Collision on an Air Track - Flash Animation

Elastic and Inelastic Collision 2- Java Applet

HyperPhysics - Elastic and Inelastic Collision

Types of Collision

Interactive Animation

Elastic and Inelastic Collision 1 - Java Applet

Collision on an Air Track - Flash Animation

Elastic and Inelastic Collision 2- Java Applet