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Energy

Energy. Momentum, Collisions, Impulse. Momentum. A measure of how hard it is to stop a moving object Momentum = (MASS) (VELOCITY). Momentum. Equation p= m v Units p= mv = (kg)(meter ) = kg ·m second s. Momentum animations.

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Energy

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  1. Energy Momentum, Collisions, Impulse

  2. Momentum • A measure of how hard it is to stop a moving object • Momentum = (MASS) (VELOCITY)

  3. Momentum Equation p= m v Units p= mv = (kg)(meter) = kg·m second s

  4. Momentum animations • http://physics.weber.edu/amiri/director/Momentum.html

  5. Momentum Example 1 What is the momentum of an orange with a mass of 0.5kg thrown with a velocity of 5.0 m/s? m = 0.5kg v = 5.0 m/s p = mv = (0.5kg)(5.0 m/s) = 2.5 kg·m s

  6. Momentum Example 2 An object with a mass of 3.0 kg is traveling at a velocity of 4.0 m/s . What is its momentum?

  7. More momentum examples • http://id.mind.net/~zona/mstm/physics/mechanics/momentum/introductoryProblems/momentumSummary1.html

  8. Conservation of Momentum Newton’s Third Law For every action there is an equal and opposite reaction! • To accelerate an object, we must apply force

  9. Conservation of Momentum • Force(s) must be external • Internal forces do not apply E.g. to accelerate a car, do you push on the dashboard?

  10. Conservation of Momentum • http://id.mind.net/~zona/mstm/physics/mechanics/momentum/introductoryProblems/momentumSummary3.html

  11. Collisions Net momentum before collision = Net momentum after the collision

  12. Elastic Collisions • http://id.mind.net/~zona/mstm/physics/mechanics/momentum/solvers/momentumSolvers1.htm

  13. Inelastic Collisions • http://id.mind.net/~zona/mstm/physics/mechanics/momentum/solvers/momentumSolvers1.htm

  14. Impulse = force exerted over time Impulse changes momentum

  15. Impulse Equation J = (Force) (time) J = Ft = mΔv = Δp = m (v2-v1) = Δp (mass)(change in velocity) = change in momentum

  16. Impulse Units J= (Newton) (seconds) J = N·s • Force is in Newtons • Time is in seconds

  17. Impulse Example An 8N force acts on a 5 kg object for 3 seconds. If the initial velocity of the object was 25 m/s, what is its final velocity? F= 8 N m= 5 kg t= 3 s v1 = 25 m/s v2= ? J = Ft =(8N)(3s) = 24 N·s BUT we need to find v2 ………

  18. Impulse Example J = mΔv = m (v2-v1) = 24 N·s = 5 kg(v2 - 25 m/s) = 24 = 5 v2- 125 m/s = 125+24= 5 v2 = 149/5 = v2 = 29.8 m/s

  19. Impulse problems • http://id.mind.net/~zona/mstm/physics/mechanics/momentum/introductoryProblems/momentumSummary2.html

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