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Linear Momentum-solutions

# Linear Momentum-solutions - le(txl65 Linear Momentum...

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le (txl65) – Linear Momentum – mohanty – (81440) 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points 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 = 0 correct 2. v 3 m = v 3. v 3 m = 2 v 4. v 3 m = 2 3 v 5. v 3 m = 3 2 v 6. v 3 m = 1 2 v 7. v 3 m = 8. v 3 m = 3 v 9. v 3 m = 4 v 10. v 3 m = 1 3 v Explanation: Let : v 1 = v , v 2 = v , m 1 = m and m 2 = 3 m . BasicConcepts: 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 m v 6 m v + m v + 3 m v m + 3 m = 0 . AlternativeSolution: 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 = m v + 3 m ( v ) m ( v v ) m + 3 m = m ( v 3 v + v + v ) 4 m = 0 . 002 10.0points A 6 kg steel ball strikes a wall with a speed of 9 . 26 m / s at an angle of 35 . 6 with the normal to the wall. It bounces off with the same speed and angle, as shown in the figure.

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le (txl65) – Linear Momentum – mohanty – (81440) 2 x y 9 . 26 m / s 6 kg 9 . 26 m / s 6 kg 35 . 6 35 . 6 If the ball is in contact with the wall for 0 . 251 s, what is the magnitude of the average force exerted on the ball by the wall?
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Linear Momentum-solutions - le(txl65 Linear Momentum...

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