Lect_20 - Example: Elastic collision What is the velocity...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 20 Center of Mass Example: Elastic collision A. 2.0 m/s, 10 m/s B. 5.3 m/s, 2.7 m/s C. -5.3 m/s, 2.7 m/s D. -3.3 m/s, 2.7 m/s E. -3.3 m/s, 4.7 m/s What is the velocity of each block if the collision is elastic? v 1 = 10 m/s 2 = 2.0 m/s 1 kg 5 kg Before 11 22 mv ′′ +=+ () 12 vv −= −− 1 = 10 m/s 2 = 2.0 m/s 1 kg 5 kg Before 1 2 1 kg 5 kg After 10 10 5 10 2 − − 20 5 8 =− 8 20 5 8 2 28 4.7 m/s 6 == Answer: E 1 3.3 m/s ′=− Example: Ballistic pendulum Example: Ballistic pendulum Let’s go back to the bullet and block example…
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
v m M At rest Before v’ After M + p total, initial = mv + 0 total, final = ( + m)v’ vv Mm ′ = + = ( + Now we’ll do the same thing with the block hanging from two strings of length L. + After At rest Before L + After after L-h Between “ before ” and “ after ”, the collision is exactly the same as for the block on the table. + After At rest Before ′ = + Linear momentum is conserved. Between “ after ” and “ after-after ”, momentum is not conserved ( F ext 0). But only conservative forces are doing work, so E is conserved . () 2 1 00 2 Mmv Mmgh ++ = + + 22 11 1 Note that ( ) 2 1 (some energy is lost in the collision) vm m gh   += = < +  + 2 2 h g = 2 2 2 = + + After + After after
Background image of page 2
ACT: Ballistic pendulum ACT: Ballistic pendulum The projectile is a ball with two sides. One is smooth and the other has two spikes, so the ball sticks to the wooden block. In which case will the block move higher?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/16/2008 for the course PHYSICS 221 taught by Professor Johnson during the Fall '06 term at Iowa State.

Page1 / 6

Lect_20 - Example: Elastic collision What is the velocity...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online