Elastic collision what is conserved

The result of this example is intuitively reasonable. A small object strikes a larger one at rest and bounces backward. The larger one is knocked forward, but with a low speed. This is like a compact car bouncing backward off a full-size SUV that is initially at rest. As a check, try calculating the internal kinetic energy before and after the collision.

You will see that the internal kinetic energy is unchanged at 4. Also check the total momentum before and after the collision; you will find it, too, is unchanged.

The equations for conservation of momentum and internal kinetic energy as written above can be used to describe any one-dimensional elastic collision of two objects. These equations can be extended to more objects if needed. Find a few ice cubes which are about the same size and a smooth kitchen tabletop or a table with a glass top. Place the ice cubes on the surface several centimeters away from each other.

Flick one ice cube toward a stationary ice cube and observe the path and velocities of the ice cubes after the collision. Try to avoid edge-on collisions and collisions with rotating ice cubes. Have you created approximately elastic collisions? Explain the speeds and directions of the ice cubes using momentum.

Investigate collisions on an air hockey table. Set up your own experiments: vary the number of discs, masses and initial conditions. Is momentum conserved? Is kinetic energy conserved? Vary the elasticity and see what happens. Skip to main content. Linear Momentum and Collisions. Search for:. Elastic Collisions in One Dimension Learning Objectives By the end of this section, you will be able to: Describe an elastic collision of two objects in one dimension.

The total system momentum is conserved. An analysis of the kinetic energy of the two objects reveals that the total system kinetic energy before the collision is Joules J for the truck plus 0 J for the car. After the collision, the total system kinetic energy is Joules J for the truck and J for the car. The total kinetic energy before the collision is equal to the total kinetic energy after the collision.

A collision in which total system kinetic energy is conserved is known as an elastic collision. For more information on physical descriptions of motion, visit The Physics Classroom Tutorial. Detailed information is available there on the following topics:. A high speed car collision is an inelastic collision. In the above example, if you calculated the momentum of the cars before the collision and added it together, it would be equal to the momentum after the collision when the two cars are stuck together.

However, if you calculated the kinetic energy before and after the collision, you would find some of it had been converted to other forms of energy. An elastic collision occurs when the two objects "bounce" apart when they collide. Two rubber balls are a good example. In an elastic collision, both momentum and kinetic energy are conserved. Almost no energy is lost to sound, heat, or deformation.