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# 23 - fryer(vdf96 Conservation of Momentum graves(6 This...

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fryer (vdf96) – Conservation of Momentum – graves – (6) 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(part1of3)10.0points Assume: The bullet penetrates into the block and stops due to its friction with the block. The compound system of the block plus the bullet rises to a height of 18 cm along a circu- lar arc with a 32 cm radius. Assume: The entire track is frictionless. A bullet with a m 1 = 30 g mass is fired horizontally into a block of wood with m 2 = 4 . 78 kg mass. The acceleration of gravity is 9 . 8 m / s 2 . 32 cm 4 . 78 kg 30 g v bullet 18 cm Calculate the total energy of the composite system at any time after the collision. Correct answer: 8 . 48484 J. Explanation: Let : r = 32 cm = 0 . 32 m , h = 18 cm = 0 . 18 m , m block = 4 . 78 kg , and m bullet = 30 g = 0 . 03 kg . The mechanical energy is conserved after collision. Choose the position when the sys- tem stops at height h , where the kinetic en- ergy is 0 and the potential energy is given by ( m bullet + m block ) g h = 8 . 48484 J , which is the total energy after collision. 002(part2of3)10.0points Taking the same parameter values as those in Part 1, determine the initial velocity of the bullet. Correct answer: 301 . 154 m / s. Explanation: During the rising process the total energy is conserved E i = 1 2 ( m bullet + m block ) v 2 f and E f = ( m bullet + m block ) g h , so v f = radicalbig 2 g h = radicalBig 2 (9 . 8 m / s 2 ) (0 . 18 m) = 1 . 8783 m / s . The linear momentum is conserved in a colli- sion. p i = m bullet v i p f = ( m bullet + m block ) v f . Therefore v i = m bullet + m block m bullet v f = (0 . 03 kg) + (4 . 78 kg) (0 . 03 kg) × (1 . 8783 m / s) = 301 . 154 m / s . 003(part3of3)10.0points Denote v bullet to be the initial velocity, find the momentum of the compound system im- mediately after the collision. 1. p f = m block v bullet 2. p f = m bullet + m block v bullet 3. p f = ( m bullet + m block ) radicalbig g h 4. p f = m bullet + m block g h 5. p f = m block radicalbig g h

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fryer(vdf96)–ConservationofMomentum–graves–(6) 2 6. p f = 1 2 ( m bullet + m block ) v bullet 7. p f = 1 2 ( m bullet + m block ) radicalbig g h 8. p f = m bullet radicalbig g h 9. p f = m bullet v bullet correct 10. p f = ( m bullet + m block ) v bullet Explanation: As in part 2, due to conservation of linear momentum, p f = p i = m bullet v bullet . 004(part1of2)10.0points A student performs a ballistic pendulum experiment using an apparatus similar to that shown in the figure. Initially the bullet is fired at the block while the block is at rest (at its lowest swing point). After the bullet hits the block, the block rises to its highest position, see dashed block in the figure, and continues swinging back and forth. The following data is obtained: the maximum height the pendulum rises is 3 . 8 cm, the mass of the bullet is 88 g, and the mass of the pendulum bob is 901 kg. The acceleration of gravity is 9 . 8 m / s 2 .
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23 - fryer(vdf96 Conservation of Momentum graves(6 This...

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