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Unformatted text preview: madrid (tmm2353) HW 62 Antoniewicz (56445) 1 This printout should have 19 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 4) 2.0 points An object at location ( 17 , , ) m moves to location ( 25 , , ) m. While it is moving it is acted on by a constant force of ( 23 , , ) N. How much work is done on the object by this force? Correct answer: 184 J. Explanation: W = vector F vectorr = F x x + F y y + F z z = (23 N )( 25 ( 17))m = 184 002 (part 2 of 4) 1.0 points Does the kinetic energy of the object increase or decrease? 1. Increase 2. There is no change in the kinetic energy of the ball. 3. Decrease correct Explanation: Consider the update form of the Conserva tion of Energy: E sys,f = E sys,i + W surr . The system is the object, and the surroundings are doing work on the object. The calculated work due to the force on the object is neg ative. This means that the initial energy of the system is greater than the final energy of the system, i.e. the energy of the system de creased. The force acts on the object in a direction that opposes the initial motion of the object. Thus, the kinetic energy of the object decreases. 003 (part 3 of 4) 2.0 points Now, consider a different object as it moves from location ( 25 , , ) m to location ( 17 , , ) m. While it is moving, it is acted on by a constant force of ( 23 , , ) N. How much work is done on the second object by this force? Correct answer: 184 J. Explanation: W = vector F vectorr = F x x + F y y + F z z = (23 N )( 17 ( 25))m = 184 004 (part 4 of 4) 1.0 points Does the kinetic energy of the second object increase or decrease? 1. There is no change in the kinetic energy of the ball. 2. Increase correct 3. Decrease Explanation: Apply the update form of the Conservation of Energy once again. The work calculated is positive, so the final energy state will have a greater value than the initial energy state. 005 (part 1 of 4) 2.0 points A ball of mass 0 . 8 kg falls downward. Initially, you observe it to be 4 . 25 m above the ground. After a short time, the ball is just about to hit the ground. During this interval, how much work was done on the ball by the gravitational force? Use 9 . 8 m s 2 as the acceleration due to gravity. Correct answer: 33 . 32 J. Explanation: W = vector F vectorr = F y y madrid (tmm2353) HW 62 Antoniewicz (56445) 2 = mg ( y f y i ) = (0 . 8 kg) parenleftbigg 9 . 8 m s 2 parenrightbigg (0 4 . 25 m) = 33 . 32 J 006 (part 2 of 4) 1.0 points Does the kinetic energy of the object increase or decrease?...
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 Fall '08
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