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MasteringPhysics: Assignment Print View .. 1 of 9 10/4/2007 3:42 PM [ Print View ] PHCC 141: Physics for Scientists and Engineers I - Fall 2007 3b. Motion in Two or Three Dimensions (long/challenging start early!) Due at 11:59pm on Monday, September 10, 2007 Hide Grading Details Number of answer attempts per question is: 5 You gain credit for: correctly answering a question in a Part, or correctly answering a question in a Hint. You lose credit for: exhausting all attempts or requesting the answer to a question in a Part or Hint, or incorrectly answering a question in a Part. Late submissions: reduce your score by 100% over each day late. Hints are helpful clues or simpler questions that guide you to the answer. Hints are not available for all questions. There is no penalty for leaving questions in Hints unanswered. Grading of Incorrect Answers For Multiple-Choice or True/False questions, you lose 100% / ( # of options - 1 ) credit per incorrect answer. For any other question, you lose 3% credit per incorrect answer. Standard projectile problems Shooting over a Hill A projectile is fired with speed at an angle from the horizontal as shown in the figure . Part A Find the highest point in the trajectory, . Hint A.1 Velocity at the top Hint not displayed Hint A.2 Which equation to use Hint not displayed Express the highest point in terms of the magnitude of the acceleration due to gravity , the initial velocity , and the angle . ANSWER: = Part B What is the range of the projectile, ? Part B.1 Find the total time spent in air Part not displayed Part B.2 Find Part not displayed Express the range in terms of , , and . ANSWER: =
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MasteringPhysics: Assignment Print View .. 2 of 9 10/4/2007 3:42 PM Consider your advice to an artillery officer who has the following problem. From his current postition, he must shoot over a hill of height at a target on the other side, which has the same elevation as his gun. He knows from his accurate map both the bearing and the distance to the target and also that the hill is halfway to the target. To shoot as accurately as possible, he wants the projectile to just barely pass above the hill. Part C Find the angle above the horizontal at which the projectile should be fired. Hint C.1 How to approach the problem In the first half of this problem, you found and in terms of and . Solve these two equations to find in terms of and . Part C.2 Set up the ratio Find the ratio of to . The only variable in your answer should be . ANSWER: = Express your answer in terms of and . ANSWER: = Recall the following trigonometry formulas: , , and . In this case, since
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