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Phys298Exam2Sp08-Solution

# Phys298Exam2Sp08-Solution - Phys 298 Brown Friday March 7...

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Phys 298 Brown Exam 2 Name _____________________________ Friday, March 7, 2008 This is a closed-book, closed-note, closed-neighbor exam. You are allowed one 3”x5” card with information, a calculator (not a computer), and your writing instruments. Multiple choice questions each have only one correct choice. Partial credit will be given on the ‘work-out’ problems. You may use the value g = 10 m/s 2 where needed. Good luck, and “May the Net Force be with you!” 1. A cannonball is shot from a cannon. If the cannonball remains intact, it should land 300 meters from where it was shot. However, the cannonball breaks during its flight into two identical halves. One half lands halfway between where it was shot and where the whole cannonball should have landed. Ignoring air resistance , how far does the other half land from where it was shot? a. 150 meters b. 300 meters c. 450 meters d. 600 meters e. No way to tell 2. A force r F = 3 ) i " 2 ) j + 5 ) k acts on a particle of mass 2 kg as it moves along a straight line from the point (1,2,2) to the point (3,4,1). What is the work done by the force on this particle during this displacement? a. -3 J b. -6 J c. 15 J d. 6 J e. 9 J The center of mass must land at 300 m. Since half falls 150 m short, the other half must land 150 m past 300 – at 450 m. The displacement was 2 i + 2 j – k. Dot this with the force and get 3 x 2 -2 x 2 + 5 x -1 = -3 J

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3. Which of the following is an example of a situation in which normal force clearly does non-zero work? a. A book slides across a horizontal, frictionless tabletop. b. A book slides across a horizontal tabletop with friction. c. A book slides down a frictionless incline. d. A book sits on the floor of an elevator going down. e. A book is in free fall. (Ignore air resistance). 4. A car moving at speed v locks its brakes and slides 20 meters on a uniform, flat, level road. How far would the car slide on the same road if it were initially traveling at speed 2 v ?
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Phys298Exam2Sp08-Solution - Phys 298 Brown Friday March 7...

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