PHYS 2 Lecture Notes - Lecture 3: Net Force, Circular Motion, Spinning Wheel
Document Summary
For non-rigid body, find the sum of all the angular momentums of all the particles. Angular momentum for rigid body rotating around a symmetry axis: If net force is zero, momentum remains constant in magnitude and direction. If net torque is zero, angular momentum remains constant in magnitude and direction. Planets orbit the sun in elliptical orbits (distance from sun to planet changes). Sun"s gravitational force on the planet is always directly towards the sun. During the orbits, the angular momentum of the planet around the sun: A spinning figure skater pulls his arms in as he rotates on the ice. At any point along the orbit, happens to his angular momentum and kinetic energy ? stays the same, increases. Linear momentum is only conserved when there are no external forces. Same magnitude, since forces and lever arm are equal. Example: whirl a ball at the end of a string. Ball moves cw around a circle at constant speed.
