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Unformatted text preview: Pickering, Tracey Homework 19 Due: Mar 8 2006, noon Inst: Drummond 1 This printout should have 7 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Two ice skaters approach each other at right angles. Skater A has a mass of 67 . 8 kg and travels in the + x direction at 1 . 16 m / s. Skater B has a mass of 102 kg and is moving in the + y direction at 1 . 73 m / s. They collide and cling together. Find the final speed of the couple. Correct answer: 1 . 13777 m / s. Explanation: From conservation of momentum p = 0 m A v A + m B v B = ( m A + m B ) v f Therefore v f = p ( m A v A ) 2 + ( m B v B ) 2 m A + m B = p (78 . 648 kgm / s) 2 + (176 . 46 kgm / s) 2 67 . 8 kg + 102 kg = 1 . 13777 m / s 002 (part 1 of 1) 10 points 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 2 cm, at the maximum height the pendulum sub tends an angle of 29 . 9 , the mass of the bullet is 90 g, and the mass of the pendulum bob is 866 g. The acceleration of gravity is 9 . 8 m / s 2 . 866 g 90 g v i v f 2 9 . 9 2 cm Determine the initial speed of the projec tile. Correct answer: 6 . 65056 m / s. Explanation: Let : = 29 . 9264 , m 1 = 90 g , m 2 = 866 g , and h = 2 cm = 0 . 02 m . The final velocity is v f = p 2 g h. Using conservation of momentum m 1 v i = ( m 1 + m 2 ) v f , so v i = ( m 1 ) + ( m 2 ) m 1 v f = ( m 1 ) + ( m 2 ) m 1 p 2 g h = (90 g) + (866 g) (90 g) q 2(9 . 8 m / s 2 )(0 . 02 m) = 6 . 65056 m / s ....
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