Chapter 9 Linear Momentum Collisions Reading assignment Chapter

Center of mass for many particles: Black board example 9. 1 Where is the

A method for finding the center of mass of any object. - Hang object

Center of mass of a solid body (uniform density)

Black board example 9. 2 A uniform square plate 6 m on a side

Motion of a System of Particles. Newton’s second law for a System of Particles

A rocket is shot up in the air and explodes. Describe the motion of

Linear Momentum The linear momentum of a particle of mass m and velocity v

From Newton’s second law: The time rate of change in linear momentum is equal

Conservation of _____ momentum Thus: If no _________ is acting on a particle, it’s

Black board example 9. 3 You (100 kg) and your skinny friend (50. 0

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Chapter 9: Linear Momentum & Collisions Reading assignment: Chapter 9. 5 -9. 7 Homework : (due Wednesday, Oct. 5, 2005): Problems: 32, 36, 43, 52, 69, 71 • Center of mass • Momentum is conserved

Center of mass for many particles: Black board example 9. 1 Where is the center of mass of the arrangement of particles below. (m 3 = 2 kg and m 1 = m 2 = 1 kg)?

A method for finding the center of mass of any object. - Hang object from two or more points. - Draw extension of suspension line. - Center of mass is at intercept of these lines.

Center of mass of a solid body (uniform density)

Black board example 9. 2 A uniform square plate 6 m on a side has had a square piece 2 m on a side cut of it. The center of that piece is at x = 2 m, y = 0. The center of the square plate is at x = y = 0. Find the coordinates of the center of mass of the remaining piece.

Motion of a System of Particles. Newton’s second law for a System of Particles The ______ of a system of particles (combined mass M) moves like one equivalent particle of mass M would move under the influence of an external force.

A rocket is shot up in the air and explodes. Describe the motion of the center of mass before and after the explosion.

Linear Momentum The linear momentum of a particle of mass m and velocity v is defined as The linear momentum is a vector quantity. It’s direction is along v. The components of the momentum of a particle:

From Newton’s second law: The time rate of change in linear momentum is equal to the net forces acting on the particle. This is also true for a system of particles: Total momentum = Total mass ·velocity of center of mass And: Net external force = ______ in momentum of the center of mass

Conservation of _____ momentum Thus: If no _________ is acting on a particle, it’s momentum is conserved. This is also true for a system of particles: If no external forces interact with a system of particles the total momentum of the system remains constant.

Black board example 9. 3 You (100 kg) and your skinny friend (50. 0 kg) stand face-to-face on a frictionless, frozen pond. You push off each other. You move backwards with a speed of 5. 00 m/s. (a) What is the total momentum of the you-and-your-friend system? (b) What is your momentum after you pushed off? (c) What is your friends speed after you pushed off?