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Unformatted text preview: alexander (jra2623) oldhomework 19 Turner (92510) 1 This printout should have 10 questions. Multiplechoice 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 xaxis 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....
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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.
 Summer '08
 Kaplunovsky
 Mass, Work

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