During a collision, does an object always encounters an impulse and a change in momentum?
Yes. There is no way that a collision can produce zero impulse. (no change in momentum)
This is because of how momentum and impulse are defined:
- For there to be zero change in an object's momentum during an interval, both its mass and its velocity must remain unchanged. Remember, velocity and momentum are vector quantities, so simply retaining the same speed won't work - the object also needs to continue motion in the same direction.
For colliding objects to continue in the same direction at the same speed, they would need to pass through each other... which just isn't possible.