1. The document discusses central forces and motion under central forces. A central force is directed toward a fixed point called the center. Central forces conserve angular momentum. 2. Motion under a central force can be described using polar coordinates. The angular momentum is constant, so the radius and momentum vectors lie in a plane perpendicular to the angular momentum. 3. Important characteristics of motion under a central force include: the energy of the system is conserved, and the radius vector traces out equal areas in equal intervals of time, known as the law of equal areas.

1. Sesion #23-24 MekanikaKlasik Riser Fahdiran, M.Si Umiatin, M.Si JurusanFisika FakultasMatematikadanIlmuPengetahuanAlam

2. Outline Central Force Characteristic of Motion under Central Force 05/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 2

3. 1. Central Force A central force acting on a particle is one that is always directed toward a fixed point called the center of the force. If interaction between two objects is represented by a central force, then the force is directed along the line joining the centers of the two objects. 05/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id | 3

7. Substitute into :

14. We get :

15. If the motion is periodic of period T19 05/01/2011 © 2010 Universitas Negeri Jakarta | www.unj.ac.id |

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