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Momentum & Collisions

Momentum & Collisions. By Jennifer Pogue. Linear Momentum. Defined as mass of object times the velocity of the object The unit is This is a vector quantity which means. Momentum Components. We can break momentum into its ____________________________. Impulse.

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Momentum & Collisions

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  1. Momentum & Collisions By Jennifer Pogue

  2. Linear Momentum • Defined as mass of object times the velocity of the object • The unit is • This is a vector quantity which means...

  3. Momentum Components • We can break momentum into its ____________________________

  4. Impulse • To change an object’s momentum, a force must be applied. The force can ___________________________ the motion of the object. • If we can __________ the amount of time over which the momentum is changed, the force is _________________. this is why we have seatbelts and air bags

  5. Newton Alternative ?! If F = ma, then

  6. Impulse Equation • Since impulse (J) is defined as the change in momentum our equation is • Do the units work?

  7. Impulse-Momentum Theorem • States the impulse of the force acting on an object equals the __________ _____________________________ • We can use average force if it is not constant.

  8. Graphical Relationships • What does a Force vs time graph tell you?

  9. Real World Applications • Baseball • Seat Belt • Air Bag • Movie Stunts

  10. Conservation of Momentum • In an ________ system, momentum of a collision is _________________. • No _________________forces • A collision may be the result of physical contact between two objects • “Contact” may also be from interaction of electrons

  11. The formula • This means the total momentum before the collision equals the total momentum after the collision • Momentum is conserved in ALL collisions

  12. Types of Collisions • ________________Collision • ______________ is conserved • ______________ is not conserved as some of it is converted to other types of energy (heat, sound, work, etc) resulting in permanent deformation of the object remember the audi? • Perfectly inelastic collisions occur when the objects ______________

  13. The math? Momentum conserved looks like

  14. Types of Collisions cont 2. _________________Collision • __________________ is conserved • __________________ is conserved (You may get two equations and two unknowns.)

  15. Crash Testing • What do you notice?

  16. Car Design? • What’s the purpose of a crumple zone? • What would happen if the car was made of rubber and everything bounced off readily? • What would happen if it was completely rigid? • Think about a hamster in it’s little ball…

  17. In Summary… • Impulse • The goal is to increase the time over which the momentum of an object is changed—this lessens the force • Momentum • Inelastic—stick together • Only momentum conserved • Elastic—bounce off • Momentum & Kinetic energy conserved

  18. The Equations J = FΔt = Δp p = mv K = ½ mv2

  19. Examples A baseball of mass 145 g collides with a bat. The initial speed of the ball is 5.0 mi/hr (42.5 m/s). The final speed is 115 mi/hr (51.4 m/s). If the collision lasts for 1.20 ms, what is the impulse on the bat?

  20. Another…. Mr. Bywaters is in his truck (2800. kg) stopped at a red light. Mrs. Pogue hits him from behind in her geo metro (900. kg). If her speed before the collision is 20.0 m/s, what is the speed of the entangled cars after the collision?

  21. Let’s do one more…. A bumper car traveling 1.24 m/s hits an identical car at rest. What are the velocities of both cars after the elastic collision? (Hint: m1 = m2)

  22. One More…. A 1500. kg car traveling east with a velocity of 25.0 m/s runs a red light. It collides with a 2500. kg van traveling north at 20.0 m/s. If the collision is inelastic, what is the direction and velocity of the wreckage after the collision?

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