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Momentum

Learn about the concept of momentum and impulse in physics, including their definitions, units, and calculations. Discover how momentum changes with varying forces and velocities, as well as the nature of momentum in different collisions. Practice problems and interactive videos are included.

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Momentum

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  1. Momentum Physics I FoxTrot: Bill Amend

  2. m = 1000 kg v = 16 m/s Momentum Defined Momentumpis defined as the product of mass and velocity, mv.Units: kg m/s p = mv Momentum p = (1000 kg)(16 m/s) p = 16,000 kg m/s Author: Tippens, P. (2007)

  3. F Dt Impulse J is a force F acting for a small time interval Dt. IMPULSE Impulse: J = F Dt Author: Tippens, P. (2007)

  4. F Dt Example 1:The face of a golf club exerts an average force of 4000 N for 0.002 s. What is the impulse imparted to the ball? What is the unit for Impulse? Derive the unit from the equation. Ans: 8 Ns Author: Tippens, P. (2007)

  5. Impulse from a Varying Force Normally, a force acting for a short interval is not constant. It may be large initially and then play off to zero as shown in the graph. The average force acting over an interval of time gives the same impulse as the actual force. Impulse

  6. F Impulse Changes Velocity Consider a mallet hitting a ball: Impulse = Change in “mv” Author: Tippens, P. (2007)

  7. F Dt mv Impulse and Momentum Impulse = Change in momentum F Dt = mvf - mvo A force F acting on a ball for a time Dtincreases its momentum mv. Author: Tippens, P. (2007)

  8. The Physics Classroom. [Animations].

  9. + vf vo Vector Nature of Momentum Consider the change in momentum of a ball that is dropped onto a rigid plate: A 2-kg ball strikes the plate with a speed of 20m/s and rebounds with a speed of 15 m/s. What is the change in momentum? Author: Tippens, P. (2007)

  10. Impluse Sample Problem An 18,000 kg bus is moving with a speed of 15 m/s. If Superman is to stop the bus in 5 seconds, what average force must he exert on the bus? Explain why Superman’s force is negative?

  11. + m = 0.5 kg F 40 m/s 20 m/s Dt Your Turn!A 500-g baseball moves to the left at 20m/s striking a bat. The bat applies a force of 5000 N on the ball , and it leaves in the opposite direction at 40 m/s. What was the time of contact? Pause for Practice + - Ans: 0.006 sec Author: Tippens, P. (2007)

  12. Bellringer Questions You have 2 minutes to answer the following questions. • Momentum is a __ quantity. A. Scalar B. vector 2. If you increase the time of impact, then you can ___ the amount of force when applying an impulse. A. Increase B. decrease C. not change • A 2 kg mass moves right with a speed of 1 m/s and rebounds with a speed of 2 m/s. What is the change in momentum? A. 0 kg m/s B. 2 kg m/s C. 6 kg m/s

  13. vB vA B A B vA vB B A Conservation of Momentum The total momentum AFTER a collision is equal to the total momentum BEFORE.

  14. Types of Collisions: Elastic Collision – Total Momentum and Kinetic Energy is Conserved. Objects do not stick together The Physics Classroom. [Animations].

  15. Elastic Collision – Total Momentum and Kinetic Energy is Conserved. Objects do not stick together The Physics Classroom. [Animations].

  16. Types of Collisions: 2. Perfectly Inelastic Collision – Only Momentum is Conserved and the objects stick together. The Physics Classroom. [Animations].

  17. Name the type of collision. • What is the momentum of the system before collision? • What is the final velocity of the system after collision?

  18. M2 V2f? M1 Momentum & Impulse - Sample Problems A 30 kg mass traveling north at 40 m/s collides head on with a 60 kg mass traveling south at 50 m/s. After the collision the 30 kg mass moves south at 50 m/s. What is the velocity of the 60 kg mass after the collision? Before After Collision Collision

  19. Your Turn! A 0.105 kg hockey puck moving at 48 m/s is caught by a 75 kg goalie at rest. With what speed does the goalie slide on the ice? Pause for Practice 48 m/s Ans: 0.067 m/s

  20. Your Turn! Determine the post-collision velocity.

  21. (Save for class!) A 1 kg gun fires a 5 g bullet at a speed of 180 m/s. What is the recoil velocity of the gun?

  22. Save for class! A 0.112-kg billiard ball moving at 154 cm/s strikes a second billiard ball of the same mass moving in the opposite direction at 46 cm/s. The second billiard ball rebounds and travels at 72 cm/s after the head-on collision. Determine the post-collision velocity of the first billiard ball

  23. Bellringer Questions You have 2 minutes to answer the following questions. Answer individually! • Impulse equals change in momentum. A. True B. False 2. A 500 kg cart is traveling at 10 m/s. What is its momentum? • Which leads to a greater impulse? A. A car sticking to a wall B. A car rebounding off the wall

  24. Collision Videos Racquet ball Alciatore, D. High Speed Video Clips

  25. Jello Drop Alciatore, D. High Speed Video Clips

  26. Water balloon Alciatore, D. High Speed Video Clips

  27. Soccer Ball Kick Alciatore, D. High Speed Video Clips

  28. Foot Stomp Alciatore, D. High Speed Video Clips

  29. Fist Bounding Alciatore, D. High Speed Video Clips

  30. Rubber ball Alciatore, D. High Speed Video Clips

  31. Gun Recoil Alciatore, D. High Speed Video Clips

  32. Water Balloon and Pin Alciatore, D. High Speed Video Clips

  33. Water Balloon Pop Alciatore, D. High Speed Video Clips

  34. YouTube.com

  35. Credits: Alciatore, D.(n.d.). High Speed Video Clips. Colorado State University. Retrieved with permission from http://high_speed_video.colostate.edu/ Cutnell & Johnson Physics. (2004). [Text Art CD]. John Wiley & Sons. Foxtrot Cartoon: Bill Amend. Received from 2007 AP Conference Complimentary Resource CD. Tippens, P. (2007). Chapter 9A Impulse and Momentum. [PowerPoint Slides]. Received from 2007 AP Conference Complimentary Resource CD. The Physics Classroom. [Animations]. http://www.thephysicsclassroom.com

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