# Chapter 7 – Momentum and Impulse

•If the time interval is longer the force can be smaller yet still produce the same impulse and change in momentum •Impulse-momentum principle: the change in momentum is equal to the impulse, a different way of stating newtons second law •Conservation of momentum: if the net external force acting on a system of objects is zero the total momentum of the system is conserved. When the changes in momentum of different parts of a system cancel each other by Newton’s third law. Ig there are no external forces acting on the system, its total momentum is conserved. •Recoil: objects push against one another, moving in opposite directions. If external fore can be neglected, momentum is conserved. The total momentum before and after the interaction equals zero. After the interaction the two objects move away with equal but oppositely directed momentum vecotrs that cancel one another. •The momentum gained by the rocket in the foreward direction will equal in magnitude and momentum of the exhaust gases in the opposite direction. •The smaller skaters velocity will be twice as large as the larger skaters velocity. •Perfectly inelastic collision: objects stick together and have 1 final velocity. •Elastic collision: no energy is lost the objects bounce; partially inelastic some initial kinetic energy is lost. The magnitude of the balls velocity will be less after the collision. •Angle: when objects collide at an angle the total momentum of the system before and after the collision is found by adding the momentum vectors of the individual objects

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