Inelastic Collisions

Perfectly elastic collisions are those in which no kinetic energy is lost in the collision. Macroscopic collisions are generally inelastic and do not conserve kinetic energy, though of course the total energy is conserved as required by the general principle of conservation of energy. The extreme inelastic collision is one in which the colliding objects stick together after the collision, and this case may be analyzed in general terms:

Calculation

Derivation of kinetic energy loss expressions

Examples of inelastic collisions

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K.E. Lost in Inelastic Collision

In the special case where two objects stick together when they collide, the fraction of the kinetic energy which is lost in the collision is determined by the combination of conservation of energy and conservation of momentum.

One of the practical results of this expression is that a large object striking a very small object at rest will lose very little of its kinetic energy. If your car strikes an insect, it is unfortunate for the insect but will not appreciably slow your car. On the other hand, if a small object collides inelastically with a large one, it will lose most of its kinetic energy.

Calculation

Velocity after the collision

Examples of inelastic collisions

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Inelastic Collision Examples

Most ordinary collisions are classified as inelastic collisions because some of their kinetic energy is converted to other forms such as internal energy. Links to some examples are provided.

Car crash

Seatbelts

Airliner and duck

Ballistic pendulum

One dimensional

Two dimensional

Franck-Hertz experiment

Two-truck collision

 Index

Collision concepts

Inelastic collisions
 
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