Collision - Practice Questions & MCQ

The interaction between two or more objects is called a collision.And during this interaction strong force acts between two or more bodies for a short time as a result of which the energy and momentum of the interacting particle change.

•  Stages of collision-

There are three distinct identifiable stages in collision

1. Before the collision.-

The interaction forces are zero

2. During the collision-

The interaction forces are very large and this forces act for a very short time. And because of this interaction forces the energy and momentum of the interacting particle change.

3. After the collision-

The interaction forces are zero

•  Momentum and energy conservation in collision

The magnitude of the interacting force is often unknown, therefore, Newton’s second law cannot be used. But the law of conservation of momentum is useful in relating the initial and final velocities.

1.  Momentum conservation-

 In a collision the effect of external forces such as gravity or friction is not taken into account as due to small duration of collision (t) average impulsive force responsible for collision is much larger than external force acting on the system and since this impulsive force is 'Internal' therefore the total momentum of the system always remains conserved.

2. Energy conservation-

In a collision 'total energy' is also always conserved. Here total energy includes all forms of energy such as mechanical energy, internal energy, excitation energy, radiant energy, etc.

But in a collision Kinetic energy may or may not be conserved.

• Coefficient of restitution-

The ratio of the relative velocity of separation to the relative velocity of approach. 

                                  $e=\frac{v_2-v_1}{u_1-u_2}=\frac{\text { Relative velocity of separation }}{\text { Relative velocity of approach }}$