oldhw 19 - alexander (jra2623) oldhomework 19 Turner...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

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

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

Unformatted text preview: alexander (jra2623) oldhomework 19 Turner (92510) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Two particles of masses m and 3 m are moving toward each other along the x-axis with the same speed v . They undergo a head- on elastic collision and rebound along the x- axis. m v 3 m v Determine the final speed of the heavier object. 1. v 3 m = 4 v 2. v 3 m = 3 2 v 3. v 3 m = 4. v 3 m = 2 3 v 5. v 3 m = 1 2 v 6. v 3 m = 0 correct 7. v 3 m = v 8. v 3 m = 2 v 9. v 3 m = 1 3 v 10. v 3 m = 3 v Explanation: Let : v 1 = v , v 2 =- v , m 1 = m and m 2 = 3 m. Basic Concepts: Conservation of momentum Solution: Denote the smaller mass initially moving to the right as m 1 and the larger mass initially moving to the left as m 2 . Since no external forces act on the two masses, even during the collision, the total momentum is conserved. Also, since the masses collide elastically, en- ergy is conserved. Since this is a head on, elastic collision we can use v 2 = 2 v cm- v 2 , where v cm = m 1 v 1 + m 2 v 2 m 1 + m 2 , so v 2 = 2 m 1 v 1 + 2 m 2 v 2 m 1 + m 2- v 2 ( m 1 + m 2 ) m 1 + m 2 = 2 mv- 6 mv + mv + 3 mv m + 3 m = . Alternative Solution: From the relative velocities formula, v 1- v 2 = v 2- v 1 . (1) From conservation of momentum, m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 . (2) Combining Eqs. 1 and 2 gives m 1 v 1 + m 2 v 2 = m 1 ( v 2 + v 2- v 1 ) + m 2 v 2 , v 2 = m 1 v 1 + m 2 v 2- m 1 ( v 2- v 1 ) m 1 + m 2 = mv + 3 m (- v )- m (- v- v ) m + 3 m = m ( v- 3 v + v + v ) 4 m = . 002 10.0 points Two ice skaters approach each other at right angles. Skater A has a mass of 76 . 8 kg and travels in the + x direction at 2 . 03 m / s. Skater B has a mass of 61 . 1 kg and is moving in the + y direction at 2 . 38 m / s. They collide and cling together. Find the final speed of the couple. alexander (jra2623) oldhomework 19 Turner (92510) 2 Correct answer: 1 . 54602 m / s....
View Full Document

This note was uploaded on 10/20/2011 for the course PHY 302K taught by Professor Kaplunovsky during the Summer '08 term at University of Texas at Austin.

Page1 / 5

oldhw 19 - alexander (jra2623) oldhomework 19 Turner...

This preview shows document pages 1 - 3. Sign up to view the full document.

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