Increasing the time of impact reduces the force experienced, given a constant impulse (change in momentum).

The object experiences an impulse, resulting in a change in its momentum.

The total momentum remains constant (is conserved).

Linear momentum ($\vec{p}$) is a measure of how much 'oomph' an object has in its motion. It's the product of an object's mass ($m$) and its velocity ($\vec{v}$). $\vec{p} = m \vec{v}$

Impulse ($\vec{J}$) is the change in momentum of an object. It's also equal to the net force ($\vec{F}$) acting on an object multiplied by the time interval ($\Delta t$) over which the force acts. $\vec{J} = \vec{F} \Delta t$

A collision in which kinetic energy is conserved. Objects bounce off each other without losing energy to heat or deformation.

A collision in which kinetic energy is not conserved. Some kinetic energy is converted into other forms of energy, such as heat or sound. Objects may stick together after the collision.

A special type of inelastic collision where objects stick together after colliding.

Reduces the force experienced by the objects involved, given the impulse remains the same.

Increases the impulse and thus the change in momentum of the object.

The total momentum remains constant; it is conserved.

It is a perfectly inelastic collision, and kinetic energy is not conserved.

External forces prevent the conservation of momentum within the system.