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ap-physics-b-review-energy-and-momentum

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AP physics
Momentum and energy

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ap-physics-b-review-energy-and-momentum

  1. 1. AP Phys B Test Review Momentum and Energy 4/28/2008
  2. 2. Overview  Momentum • Center of Mass • Impulse-Momentum Theorem • Conservation of Momentum  Energy • Work-Energy Theorem • Conservation of Energy • Elastic and Inelastic Collisions
  3. 3. Momentum  Momentum • Momentum is defined as: • The rate of change of momentum of an object is equal to the net force applied to the object.   p m v= Σ ∆ ∆   F p t =
  4. 4. Conservation of Momentum  Conservation of momentum states that: the total momentum of an isolated system of objects remains constant. • Isolated system: no outside forces acting on the system • Tip: Break the momentum of each component up into horizontal and vertical components: these are independent of one another!
  5. 5. Collisions and Impulse  Impulse-momentum theorem defines impulse and says that the impulse on a system will be equal to the change in its momentum.   F t p∆ ∆=
  6. 6. Center of Mass  The center-of-mass of a collection of particles if given by the following equation: • The total linear momentum of a system of particles is equal to the total mass M of the system multiplied by the velocity of the center of mass of the system. • Extended systems use this formulation for Newton’s Laws too. x M m xC M i i= 1 Σ
  7. 7. Work and Energy  Work is merely a force applied on an object over a certain distance.  Kinetic Energy is the energy of motion.  Potential Energy is the ability of an object to start/stop motion. • Gravity: Elastic W F d= c o s θ T m v= 1 2 2 U m g h= U k x= 1 2 2
  8. 8. Work-Energy Theorem  This principle states that the work done on an object is equal to the change in kinetic energy of an object W T= ∆
  9. 9. Conservation of Energy  Conservative vs. Non-conservative Forces • Friction  Conservation of Energy: The total energy of an isolated system cannot change. • Shift between potential and kinetic energy.
  10. 10. Power  Power is defined as energy over a given time period.
  11. 11. Collisions  Elastic Collisions • “Rubber” – things bounce off. • Both energy and momentum are conserved.  Inelastic Collisions • “Gluey” – things stick together • Only momentum is conserved!
  12. 12. Rotational Mechanics  Radians  Angular displacement, velocity, acceleration  Moment of Inertia  Torque  Angular Momentum
  13. 13. Simple Harmonic Motion  Period and Frequency  Oscillatory Motion • Springs, Pendulums • Conservation of Energy • Position as a function of time x t A t( ) c o s ( )= ω

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