Collision is a physical process in which two or more objects, either particle masses or rigid bodies, experience very high force of interaction for a very small duration. It is not essential for the objects to physically touch each other for collision to occur. Irrespective of the nature of interactive force and the nature of colliding bodies, Newton's second law holds good on the system. Hence, momentum of the system before and after the collision remains conserved if no appreciable external force acts on the system during collision.
The amount of energy loss during collision, if at all, is indeed dependent on the nature of colliding objects. The energy loss is observed to be maximum when objects stick together after collision. The terminology is to define collision as 'elastic' if no energy loss takes place and to define collision as 'plastic' for maximum energy loss. The behaviour of system after collision depends on the position of colliding objects as well. A unidirectional motion of colliding objects before collision can turn into two dimensional after collision if the line joining the centre of mass of the two colliding objects is not parallel to the direction of velocity of each particle before collision. Such type of collision is referred to as oblique collision which may be either two or three dimensional.
Which of the following collisions is one-dimensional?

Options

A. A ball striking a rigid wall (consider ball as system)
B. A `5 kg` mass thrown vertically up exploding during its motion (`5 kg` mass is the system).
C. A particle hitting a rigid bar of length `L` lying on a frictionless surface (consider rigid bar as the system).
D. Two particles moving towards each other due to gravitational attraction and hitting each other (consider ally particle as system).

Answer

B

Explanation

`mg` is mall compared to force of explosion