In the impulse approximation, .

(A) the forces between colliding objects can be neglected
(B) the external forces acting during a collision can be neglected
(C) the momentum of an object is zero
(D) the true impulse is approximated by a rectangular pulse

(B) the external forces acting during a collision can be neglected

Explanation:

Impulse is the product of force and time for which it acts. From Newton's second law, impulse is the change in momentum. In a collision of bodies, there is a change in velocity, either in direction or magnitude. Hence, there is a change in momentum and an impulse.

The forces between the object contribute to the impulse and cannot be neglected.

Since the forces act over a time interval, they may be time-dependent. In such cases, the impulse is not a rectangular pulse (which is the graph of a time-independent force).

Impulse calculations are performed in isolated systems. Hence, external forces are neglected.

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