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Physics 121 Final Fall 2007 VERSIONA A

# Physics 121 Final Fall 2007 VERSIONA A - Physics 121 Final...

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Physics 121 Final Fall 2007 Version A Name___________________________ Student I.D.____________________________ 1) A 4 Kg object consists of two massless meter long rods, one along the x axis and one along the y axis. Each rod has a 1 Kg point mass attached to each of its ends. Initially the rods are at rest. A 0 ______ a) At t = 0 the rods start to rotate about an axis perpendicular to the rods going through their common center with an angular acceleration of 2 radians/s 2 . How large is the torque (in Nm) about the z-axis? B 1 ______ b) What is its kinetic energy (in Joules) when it goes through the angle of 25 radians? C 2 D 3 ______ 2) a) How long (in s) will it take the object of problem 1) to reach an angular velocity of 40 rad/sec? E 4 ______ b) If the rods were suddenly shrunk to 1/2 meter when they reached the angle of 25 radians, what would the new angular velocity be? (in radians/s) F 5 G 6 ______ 3) a) A cube of aluminum two meters on a side is centered at the origin. The perpendiculars to its six faces are along the + and - directions of the x, y and z axes. If forces of 1.5x10 8 Newtons each are applied in opposite outward directions along the x axis, the length of the cube along the x axis will increase by ___x10 -3 meters. Take Young's modulus for aluminum to be 2.5x10 10 Pa.

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Physics 121 Final Fall 2007 VERSIONA A - Physics 121 Final...

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