Impact:

The phenomenon of collision of two moving bodies where active and reactive forces of extremely large magnitude act on them over quite a short duration of their contact time is called impact. The duration of impact shall depend on the elastic/plastic properties of the body. The duration of impact is Δ t = (t₂ - t₁ ) seconds is normally a few milliseconds or sometimes even less than a millisecond. Large impulsive forces (that means active and reactive) are developed very fast from their zero value to their maximum value and then fall down back to zero again quickly.

Generally following two assumptions are made in the study of impact.

a. Forces other than impulsive-forces can be neglected. Gravitational forces are non-impulsive and are quite small as compared to the impulsive forces.

b. Since the time of duration of impact is very short, it can be assumed that bodies are almost motionless during this time (Δ t) of the impact.

The total impulsive force on any mass m is an integrated effect during the short period

Δ t = (t₂ - t₁ ) given by

Where, V₁ and V₂ are velocities of the mass (m) just before and after impact.