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Unformatted text preview: Morby, Grant Quiz 2 Due: Mar 8 2006, 10:00 pm Inst: Drummond 1 This print-out should have 21 questions. Multiple-choice 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 A(n) 5 . 53 g bullet is fired into a(n) 1 . 59 kg ballistic pendulum and becomes embedded in it. The acceleration of gravity is 9 . 8 m / s 2 . If the pendulum rises a vertical distance of 5 . 78 cm, calculate the initial speed of the bullet. Correct answer: 307 . 094 m / s. Explanation: Basic Concepts: Applying conservation of mechanical energy from just after the colli- sion until the end of the swing is reached, we have 1 2 ( M + m ) V 2 = ( M + m ) g h where M is the mass of the pendulum, m the mass of the bullet, h the vertical height through which the pendulum swings, and V is the velocity of the (pendulum plus bullet) immediately after the collision. The equation above reduces to V = p 2 g h. (1) Now apply conservation of momentum from just before to just after the collision. We have mv = ( M + m ) V , (2) where v is the velocity of the bullet just prior to collision. Thus, mv = ( M + m ) p 2 g h, so v = ( M + m ) m p 2 g h = (1 . 59 kg) + (0 . 00553 kg) (0 . 00553 kg) q 2(9 . 8 m / s 2 )(0 . 0578 m) = 307 . 094 m / s . 002 (part 1 of 4) 10 points The following figure shows a Ferris wheel that rotates 3 times each minute and has a diame- ter of 17 m. The acceleration of gravity is 9 . 8 m / s 2 . What is the centripetal acceleration of a rider? Correct answer: 0 . 838916 m / s 2 . Explanation: The period of the Ferris wheel is T = (60 s) (3) = 20 s . The speed of the wheel is v = 2 r T = 2 (8 . 5 m) 20 s = 2 . 67035 m / s , so the centripetal acceleration is a = v 2 r = (2 . 67035 m / s) 2 (8 . 5 m) = . 838916 m / s 2 . 003 (part 2 of 4) 10 points What force does the seat exert on a 51 kg rider at the lowest point of the ride? Correct answer: 542 . 585 N. Explanation: The force exerted by the seat balances the gravity and provides the centripetal force, so F l = m [ g + a ] = (51 kg)(9 . 8 m / s 2 + 0 . 838916 m / s 2 ) = 542 . 585 N . Morby, Grant Quiz 2 Due: Mar 8 2006, 10:00 pm Inst: Drummond 2 004 (part 3 of 4) 10 points What force does the seat exert on a 51 kg rider at the highest point of the ride? Correct answer: 457 . 015 N. Explanation: The gravity is partly balanced by the force exerted by the seat and this resultant provides the centripetal force, so F l = m [ g- a ] = (51 kg)[(9 . 8 m / s 2 )- (0 . 838916 m / s 2 )] = 457 . 015 N . 005 (part 4 of 4) 10 points What force (magnitude) does the seat exert on a rider when the rider is halfway between top and bottom?...
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This note was uploaded on 03/02/2009 for the course PHY 58235 taught by Professor Kleinman during the Spring '09 term at University of Texas at Austin.
- Spring '09