AP_Physics_Topic_5_Student_Notes.doc - Topic 5 Conservation...

This preview shows page 1 - 2 out of 19 pages.

Topic 5 Conservation of Linear Momentum I. Introduction. a. One of the most important principles in physics is the law of conservation of momentum, which says that the total momentum of a system and its surroundings does not change. Whenever the momentum of a system changes, we can account for the change by the appearance or disappearance of momentum somewhere else. b. In this chapter, we introduce the ideas of impulse and linear momentum, and show how integrating Newton’s second law produces an important theorem known as the impulse–momentum theorem. We will also determine if the momentum of a system remains constant, and how to exploit constant momentum to solve problems involving collisions between objects. In addition, we examine a new reference frame, known as the center-of-mass reference frame, and explore situations in which a system has a continuously changing mass. II. Conservation of Linear Momentum. a. When Newton devised his second law, he considered the product of mass and velocity as a measure of an object’s “quantity of motion.” Today, we call the product of a particle’s mass and velocity linear momentum b. Linear momentum is a vector quantity, it is the product of a vector (velocity) and a scalar (mass). Its magnitude is and it has the same direction as . The units of momentum are units of mass times speed, so the SI units of momentum are kg•m/s. c. Momentum may be thought of as a measurement of the effort needed to bring a particle to rest. i. Thus, the net force acting on a particle equals the time rate of change of the particle’s momentum. ii. d. The total momentum of a system of particles is the vector sum of the momenta of the individual particles. i. 1
Image of page 1

Subscribe to view the full document.

Topic 5 Conservation of Linear Momentum ii. But according to Newton’s second law for a system of particles, equals the net external force acting on the system. iii. e. When the sum of the external forces acting on a system of particles remains zero, the rate of change of the total momentum remains zero and the total momentum of the system remains constant. i. ii. This result is known as the law of conservation of momentum. iii. iv. This law is one of the most important in physics. It is more widely applicable than the law of conservation of mechanical energy because internal forces exerted by one particle in a system on another are often not conservative. The nonconservative internal forces can change the total mechanical energy of the system, though they effect no change of the system’s total momentum. If the total momentum of a system remains constant, then the velocity of the center of mass of the system remains constant. The law of conservation of momentum is a vector relation, so it is valid component by component. f. Finding Velocities Using Momentum Conservation ( Equation 8-5 ) i. PICTURE Determine that the net external force (or ) on the system is negligible for some interval of time. If the net force is determined not to be negligible, do not proceed.
Image of page 2
You've reached the end of this preview.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern