Collisions (AQA GCSE Combined Science: Trilogy): Revision Note

Collisions

• Examples of momentum in an event are collisions

• Objects will either:

  • Collide and move in opposite directions - this is an elastic colision

  • Collide and move in the same direction together - this is an inelastic collision

• When the objects move in opposite directions:

  • Each object will have a different velocity depending on its mass and initial momentum of the system

• When the objects move in the same direction together:

  • They will have a combined mass and velocity

• Momentum is always conserved in a collision

Types of collisions

If an exam question asks you to analyse a collision, follow these tips for full marks:

• Always consider the motion before and after the collision and state:

  • The velocities of each object

  • The direction each object moves

• State whether the collision was elastic or inelastic and explain your reasoning

  • In a perfectly elastic collision, the kinetic energy is the same before and after

  • In a perfectly inelastic collision, the two objects stick together after colliding

• Describe any energy transfers that occur if kinetic energy is not conserved

  • For example, it may be converted into heat, sound, elastic potential energy etc