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quiz5 - UCSD Physics 2A Fall 2009 Instructor Vivek Sharma...

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Unformatted text preview: UCSD Physics 2A Fall 2009 Instructor : Vivek Sharma Quiz Five INSTRUCTIONS: Enter your name and code # in the bottom strip of the first page. Return the entire set of exam sheets with your scantron . Use a #2 pencil to fill your scantron. Write your code number and bubble it in under ““EXAM NUMBER””. Bubble in the quiz version (see letter A--D at bottom of page) in your scantron under ““ EXAM VERSION””. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A stuntman drives a car over the top of a hill, the crosssection of which can be approximated by a circle of radius R=250m. What is the greatest speed with which he can drive without the car leaving the road at the top of the hill? A) 25 m/s B) 192 m/s C) 99 .0 m/s D) 29 m/s E) 49.5 m/s 2) A particle is moving in three-dimensions and is not acted on by any non-conservative forces. The particle is moving with velocity v when it is located at point O. When the particle returns to point O at a later time, which statement is true about its velocity? A) The magnitude of the velocity when the particle returns will be less than the magnitude of v . B) The velocity when the particle returns will again be v . C) The magnitude of the velocity when the particle returns will be greater than the magnitude of v . D) The magnitude of the velocity when the particle returns is the magnitude of v . E) Both statements A and C are true. Enter Your name and Code number Name____________________________________________Code-Number___________________ Exam Version A‐1 UCSD Physics 2A Fall 2009 Instructor : Vivek Sharma 3) You and your bicycle have combined mass 80.0kg. When you reach the base of a bridge, you are travelling along the road at 5.0m/s . At the top pf the bridge (see figure above), you have climbed a vertical distance of 5.20m and have slowed to 1.50m/s. You can ignore work done by friction and any inefficiency in the bike or your legs. How much work have you done with the force you apply to the pedals? A) +4987 J B) -4987 J C) -3170 J D) -3167 J E) +3170 J 4) Consider a wet roadway banked as in the figure., where the coefficient of static friction is 0.30 and the coefficient of kinetic friction between the tires and the road is 0.25. The radius of the curve is 50 m. If the banking angle is 25 o , what is the minimum speed the automobile can have before sliding down the banking? A) 2.09 m/s B) 0.85 m/s C) 0.209 m/s D) 8.5 m/s E) 20.9 m/s 5) Consider an object that is dropped from rest. At which point in its motion to the ground is the power generated by the gravitational force on the object the greatest? A) at the instant preceding contact with the ground B) at the instant the object is at one-half its starting height C) at the instant immediately after the objectʹs release D) The power is constant because the gravitational force on the object is constant. E) at the instant the object is 1/4 its starting height Test Version A‐2 UCSD Physics 2A Fall 2009 Instructor : Vivek Sharma 6) A small block with mass of 0.120kg is attached to a chord passing through a hole in a frictionless horizontal surface. The block is originally revolving at a distance of 0.40m from the hole with a speed of 0.70m/s. The chord is them pulled from below, shortening the radius of the circle in which the block revolves to 0.10m At this distance the speed of the block is 2.80m/s. How much work was done by the person who pulled on the cord ? A) 1.2 J B) 0.012 J C) 0.0 J D) 0.44 J 7) Two objects of equal mass move with the same kinetic energy, but one moves on a circular path of radius A and the other moves on a circular path of radius B. What is the ratio of the centripetal force on the object moving on the path of radius A to the centripetal force on the object moving on the path of radius B? C) A2 /B2 D) A/B E) B/A A) B2 /A2 B) B/A 8) A 3.00-kg ball swings rapidly in a complete vertical circle of radius 2.00 m by a light string. The ball moves so fast that the string is always taut. As the ball swings from its lowest point to its highest point: A) The work done on it by gravity is -118 J and the work done on it by the tension in the string is +118 J. B) The work done on it by gravity is -118 J and the work done on it by the tension in the string is zero. C) The work done on it by gravity is +118 J and the work done on it by the tension in the string is -118 J. D) The work done on it by gravity and the work done on it by the tension in the string are both equal to -118 J. E) The work done on it by gravity and the work done on it by the tension in the string are both equal to zero. Test Version A‐3 Question 1 2 3 4 5 6 7 8 Ver A E D E D A D E B Ver B E B E B B C D B Quiz 5 Answer Key Ver C Ver D Ver E A A A D D E C B B E B C C B B B C E D C E A B D Ver F D E D A B D D B Ver G A A C E E D D B Ver H C B B D E E B D ...
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