1 / 13

Impulse, Momentum and Collisions

Impulse, Momentum and Collisions. momentum = mass x velocity p = m v units: kgm/s or Ns. What is the value of the momentum of a 10 kg ball rolling down a bowling alley at a speed of 5 m/s?. p = mv. p = (10 kg)(5 m/s). p = 50 kgm/s. Momentum is a vector, it has a direction.

brent
Download Presentation

Impulse, Momentum and Collisions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Impulse, Momentum and Collisions

  2. momentum = mass x velocity p = mv units: kgm/s or Ns

  3. What is the value of the momentum of a 10 kg ball rolling down a bowling alley at a speed of 5 m/s? p = mv p = (10 kg)(5 m/s) p = 50 kgm/s

  4. Momentum is a vector, it has a direction The ball bounces off the wall. What is the change in momentum? Dp = pfinal - pinitial = 2p

  5. Newton’s 2nd Law: F = ma = mDv/Dt p Impulse-Momentum Theorem FDt = p

  6. If this girl throws a 0.2 kg snowball at 20 m/s…at you, and it impacts your skull for 0.05 s, what is the force of the impact? FDt = mDv F = mDv/Dt F = (0.2 kg)(20 m/s)/0.05 s F = 80 N

  7. Stopping Distance A 2500 kg car brakes to slow from 25 m/s to 10 m/s in 6 s. What was the force of braking? F = mDv/Dt = (2500 kg)(10 m/s – 25m/s)/6s F = -6250 N How far will it go in that time? Dx = ½(vi + vf)Dt = ½(25m/s + 10m/s) 6s Dx = 105 m

  8. Conservation of Momentum The total momentum before equals the total momentum after, if there are no external forces. m1v1i + m2v2i = m1v1f + m2v2f

  9. 80 kg Schoettle steps out of his 100 kg boat with a velocity of 2 m/s. What is the boat’s velocity? 0 0 m1v1i + m2v2i = m1v1f + m2v2f v2f = -m1v1f/m2 v2f = -(80 kg)(2 m/s)/100 kg v2f = 1.6 m/s

  10. Types of collisions (two things hitting each other) Perfectly Inelastic: the two things stick together m1v1i + m2v2i = (m1 + m2)vf 5 kg 10 kg What is the velocity after they stick? v1i = 3 m/s m1v1i + m2v2i = (m1 + m2)vf m1v1i = (m1 + m2)vf vf = 2 m/s

  11. Kinetic Energy is lost in inelastic collisions from the previous problem: m1 = 10 kg, v1i = 3 m/s, m2 = 5 kg, v2 = 0 How much of the KE got changed into other types of energy (sound, heat)? KEi = ½m1v1i2 = ½(10kg)(3 m/s)2 = 45 J KEf = ½(m1 + m2)vf2 = ½(10kg + 5kg)(2 m/s)2 = 30 J KEi – KEf = 15 J

  12. Elastic Collisions Two objects hit and bounce off with no damage or loss of KE or momentum momentum: m1v1i + m2v2i = m1v1f + m2v2f KE: ½m1v1i2 + ½m2v2i2 = ½m1v1f2 + ½m2v2f2

  13. Most collisions are neither elastic or perfectly inelastic.

More Related