Mastering physics assignment #9

Mastering Physics Assignment #9
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Assignment #9 Due: 11:00pm on Tuesday, July 23, 2013 You will receive no credit for items you complete after the assignment is due. Grading Policy A message from your instructor. .. ***** Note: this assignmnet is due on MONDAY March 10 ***** A Bullet Is Fired into a Wooden Block A bullet of mass is fired horizontally with speed at a wooden block of mass resting on a frictionless table. The bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block, with the bullet in it, is traveling at speed . Part A Which of the following best describes this collision? Hint 1. Types of collisions An inelastic collision is a collision in which kinetic energy is not conserved. In a partially inelastic collision, kinetic energy is lost, but the objects colliding do not stick together. From this information, you can infer what completely inelastic and elastic collisions are. ANSWER: Correct m b v i m w v f perfectly elastic partially inelastic perfectly inelastic
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Part B Which of the following quantities, if any, are conserved during this collision? Hint 1. When is kinetic energy conserved? Kinetic energy is conserved only in perfectly elastic collisions. ANSWER: Correct Part C What is the speed of the block/bullet system after the collision? Express your answer in terms of , , and . Hint 1. Find the momentum after the collision What is the total momentum of the block/bullet system after the collision? Express your answer in terms of and other given quantities. ANSWER: Hint 2. Use conservation of momentum The momentum of the block/bullet system is conserved. Therefore, the momentum before the collision is the same as the momentum after the collision. Find a second expression for , this time expressed as the total momentum of the system before the collision. Express your answer in terms of and other given quantities. ANSWER: ANSWER: kinetic energy only momentum only kinetic energy and momentum neither momentum nor kinetic energy v i m w m b p total v f = p total ( + ) m w m b v f p total v i = p total m b v i
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Correct A One-Dimensional Inelastic Collision Block 1, of mass = 5.50 , moves along a frictionless air track with speed = 15.0 . It collides with block 2, of mass = 13.0 , which was initially at rest. The blocks stick together after the collision. Part A Find the magnitude of the total initial momentum of the two-block system. Express your answer numerically. Hint 1. How to approach the problem Find the initial momentum of each block separately; then add the two momenta together. Recall that momentum is equal to mass times velocity: . ANSWER:
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