A particle of mass m moving with velocity u makes an elastic one dimensional collision with a stationary
particle of mass m They are in contact for a brief time T. Their force of interaction increases from zero to F0 linearly in time and decreases linearly to zero in further time . The magnitude of F0 is.
In one dimensional elastic collision between two equal masses, their velocities are interchanged. Therefore, change in linear momentum of any of the particle will be mu.
Now, impulse or area under F-t graph gives the change in linear momentum.
or