7-4ConservationofEnergyandMomentuminCollisions.pptVIP

Example 7-1 Example 7-2 Example 7-3 Example 7-4 Example 7-6 Example 7-6 (cont’d) Example 7-7 Example 7-8 * Chapter 7 Linear Momentum Units of Chapter 7 Momentum and Its Relation to Force Conservation of Momentum Collisions and Impulse Conservation of Energy and Momentum in Collisions Elastic Collisions in One Dimension Inelastic Collisions Collisions in Two or Three Dimensions Center of Mass (CM) CM for the Human Body Center of Mass and Translational Motion 7-1 Momentum and Its Relation to Force Momentum is a vector symbolized by the symbol p, and is defined as The rate of change of momentum is equal to the net force: This can be shown using Newton’s second law. (7-1) (7-2) For a top player, a tennis ball may leave the racket on the serve with a speed of 55 m/s (about 120 mi/h). If the ball has a mass of 0.060 kg and is in contact with the racket for about 4 ms, estimate the average force on the ball. Would this force be large enough to lift a 60 kg person? Water leaves a hose at a rate of 1.5 kg/s with a speed of 20 m/s and is aimed at the side of a car, which stops it. (That is, we ignore any splashing back.) What is the force exerted by the water on the car? 7-2 Conservation of Momentum During a collision, measurements show that the total momentum does not change: (7-3) 7-2 Conservation of Momentum More formally, the law of conservation of momentum states: The total momentum of an isolated system of objects remains constant. A 10,000. kg railroad car, A, traveling at a speed of 24.0 m/s strikes an identical car, B, at rest. If the cars lock together as a result of the collision, what is their common speed just afterward? 7-2 Conservation of Momentum Momentum conservation works for a rocket as long as we consider the rocket and its fuel to be one system, and account for the mass loss of the rocket. Calculate the recoil velocity of a 5.0 kg rifle that shoots a 0.020 kg bullet at a speed of 620 m/s. 7-3 Collisions and Impulse During a collision, objects are