Question

Given the mass of two blocks that collide, and the velocities of each block before and after the collision, be able to determine whether the collision was elastic, partially or completely inelastic, or not possible since an unnamed external force would be necessary to change the momentum, and/or kinetic energy of the system.

Please explain in simplest terms and give an example using units given.

Answer 1

A collision will be completely elastic

If both momentum and energy is conserved. In head on , perfectly elastic collisions ( where one of the object is stationary) , the velocity of first object becomes velocity of second object and vice versa.

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A partial inelastic collision is where momentum is conserved but there is a small loss in energy as the result of collision. This lost energy will be dissipated as heat or noise. The object may or may not stick together. Usually, they don't

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A completely inelastic collision is where momentum is still conserved but a lot of energy ( usually more than half) is lost. This lost energy may result in deformation of bodies, crumpling etc.

In this collision, objects stick together and move as once after the collision.

Example - a collision between clay ball and a steel ball.

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