A projectile is fired from the ground and it bursts at the highest point and explodes into two halves.We apply law of conservation of momentum in horizontal direction.Gravity is purely vertical , so we have no problem conserving momentum in horizontal direction as the velocity at highest point is purely horizontal.What if the particle bursts somewhere inbetween.i.e. before reaching its highest point?
Can we apply conservation of momentum(Note. gravity will have a non-zero component in that direction)
66Indeed we can, since the impulse of gravity will be negligible small. As a working rule, all the finite forces could be neglected for such short-duration phenomena like an explosion.
1Exactly!
(Sir you are not supposed to answer now :p Let the students have sometime to think )
I wanted to convey the exact thing..gravity is NOT an impulsiove force..
Impulsive forces bring in change in momentum in a short time because their magnitudes can go infinitely large.
Couple of examples of impulsive forces which we come across so many times
Tension in a rope
Normal reaction force