Momentum & Impulse

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Lecture slides on momentum and impulse

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Momentum & Impulse

  1. 1. Momentum
  2. 2. Momentum Sports Announcer “The New York Yankees have the momentum!” The headlines declare "Chicago Bulls Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter."
  3. 3. Momentum Momentum is a commonly used term in sports. Defined as “mass in motion.” A team that has the momentum is on the move and is going to take some effort to stop. Impulse - change in momentum. Force applied over a given amount of time. (F •t)
  4. 4. Momentum All objects have mass so all objects have momentum, if they are moving. How much momentum do objects have? Depends on two things: Mass Velocity
  5. 5. Momentum Momentum = mass • velocity In physics, momentum is shown by the lowercase “p”. p=m•v
  6. 6. Momentum
  7. 7. Momentum Units for momentum will always be: mass unit • velocity unit kg • m/s (Don’t confuse this with Newton’s) Sometimes is shown as N•s • Why?
  8. 8. Force Time
  9. 9. Momentum The unit N • s = F • t What does F • t = m • v mean? Shows the relationship between a Force unit multiplied by a time unit is the same as a velocity multiplied a mass. So…. p = m •v & p = F • t (Two equations)
  10. 10. Momentum Momentum is a vector quantity. It shows both magnitude (size) and direction. Example: A bowling ball that has a mass of 5kg moving westward at 2 m/s. In order to fully describe this motion would need to be stated: 10 kg•m/s westward
  11. 11. Momentum Objects at rest do NOT have momentum. They do not have any “mass in motion”.
  12. 12. Momentum Example 1: Determine the momentum of a ... a. 60-kg halfback moving eastward at 9 m/s. p = (60kg)(9m/s) = 540-kg•m/s (N•s) b. 1000-kg car moving northward at 20 m/s. p = (1000kg)(20m/s) = 20,000-kg•m/s (N•s) c. 40-kg freshman moving southward at 2 m/s. p = (40kg)(2m/s) = 80-kg•m/s (N•s)
  13. 13. Momentum Example 2: A car possesses 20,000 units of momentum. What would be the car's new momentum if ... a. its velocity was doubled. ANS: 40,000 units of momentum. b. its velocity was tripled. ANS: 60,000 units of momentum. c. its mass was doubled (by adding more passengers and a greater load) ANS: 40,000 units of momentum. d. both its velocity was doubled and its mass was doubled. ANS: 80,000 units of momentum.
  14. 14. Momentum Example 3: A halfback (m = 60 kg), a tight end (m = 90 kg), and a lineman (m = 120 kg) are running down the football field. Consider their ticker tape patterns below. Compare the velocities of these three players. How many times greater are the velocity of the halfback and the velocity of the tight end than the velocity of the lineman? Which player has the greatest momentum? Explain.

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