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Unformatted text preview: lavallo (jhl936) Homework 14 florin (58140) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A solid sphere of radius 23 cm is positioned at the top of an incline that makes 27 angle with the horizontal. This initial position of the sphere is a vertical distance 3 . 1 m above its position when at the bottom of the incline. The sphere is released and moves down the incline. 23 cm M 27 3 . 1m Calculate the speed of the sphere when it reaches the bottom of the incline if it rolls without slipping. The acceleration of gravity is 9 . 8 m / s 2 . The moment of inertia of a sphere with respect to an axis through its center is 2 5 M R 2 . Answer in units of m / s. 002 10.0 points The top in the figure has moment of inertia . 000638 kg m 2 and is initially at rest. It is free to rotate about the stationary axis AA . A string wrapped around a peg along the axis of the top is pulled in such a manner as to maintain a constant tension of 3 . 61 N. F A A' If the string does not slip while being un- wound, what is the angular speed of the top after 121 cm of string has been pulled off of the peg? Answer in units of rad / s. 003 10.0 points A system of two wheels fixed to each other is free to rotate about a frictionless axis through the common center of the wheels and per- pendicular to the page. Four forces are ex- erted tangentially to the rims of the wheels, as shown below. F 2 F F F 2 R 3 R What is the magnitude of the net torque on the system about the axis? 1. = 2 F R 2. = 0 3. = 5 F R 4. = 14 F R 5. = F R 004 10.0 points A rod can pivot at one end and is free to rotate without friction about a vertical axis, as shown. A force vector F is applied at the other end, at an angle to the rod. L m F If vector F were to be applied perpendicular to the rod, at what distance d from the axis lavallo (jhl936) Homework 14 florin (58140) 2 of rotation should it be applied in order to produce the same torque vector ? 1. d = L sin 2. d = L 3. d = L cos 4. d = L tan 5. d = 2 L 005 10.0 points A spool (similar to a yo-yo) is pulled in three ways, as shown below. There is sufficient friction for rotation....
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This note was uploaded on 04/09/2010 for the course PHY 58150 taught by Professor Florin during the Spring '10 term at University of Texas at Austin.
- Spring '10