final - midterm 02 PATEL, VISHAL Due: Mar 7 2007, 10:00 pm...

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Unformatted text preview: midterm 02 PATEL, VISHAL Due: Mar 7 2007, 10:00 pm 1 Question 1 part 1 of 2 5 points A spherical mass rests upon two wedges, as seen in the figure below. The sphere and the wedges are at rest and stay at rest. There is no friction between the sphere and the wedges. M The following figures show several attempts at drawing free-body diagrams for the sphere. Which figure has the correct directions for each force? Note: The magnitude of the forces are not necessarily drawn to scale. 1. weight friction friction normal normal 2. weight normal normal 3. weight normal 4. normal normal weight weight 5. Since the sphere is not moving, no forces act on it. 6. weight normal normal correct 7. normal weight weight 8. weight 9. normal normal weight weight Explanation: Weight the force of gravity pulls the sphere down. The normal force of the left wedge upon the sphere acts perpendicular to ( normal to ) their surfaces at the point of con- tact; i.e. , diagonally upward and rightward. Likewise, the normal force of the right wedge upon the sphere acts diagonally upward and leftward. Question 2 part 2 of 2 5 points The wedges themselves lie on a horizontal table. There is friction between the table and the wedges. The following figures show several attempts at drawing free-body diagrams for the left wedge. Which figure has the correct directions for each force? Note: The magnitude of the forces are not necessarily drawn to scale. midterm 02 PATEL, VISHAL Due: Mar 7 2007, 10:00 pm 2 1. normal weight friction F s p h e r e 2. normal weight friction F s p h e r e 3. normal weight F s p h e r e 4. normal weight friction F s p h e r e correct 5. normal weight F sphere f r i c t i o n 6. Since the sphere is not moving, no forces act on it. 7. normal weight F s p h e r e 8. normal weight F sphere f r i c t i o n 9. normal weight friction F s p h e r e Explanation: The wedges weight pulls it straight down. The force of the sphere upon the wedge is the reaction to the force of the wedge upon the sphere, hence vector F sphere pushes diagonally downward and leftward. The normal force of the table upon the sphere acts straight up, perpendicular to the tables horizontal surface. Finally, the friction force pushes the wedge rightward in order to prevent it from sliding to the left due to vector F sphere . Question 3 part 1 of 1 10 points A block with a pulley attached slides along a frictionless surface. It is connected by a string to a second block as shown in the pic- ture below. midterm 02 PATEL, VISHAL Due: Mar 7 2007, 10:00 pm 3 1 2 no friction Given: the mass of the first block m 1 = 8 . 01 kg; the mass of the second block m 2 = 1 . 15 kg; g = 9 . 8 m / s 2 . Both pulleys are frictionless and have negligible masses and ro- tational inertias. The string does not stretch, and its mass is negligible. There is no friction between the first block and the table....
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This note was uploaded on 03/20/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

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final - midterm 02 PATEL, VISHAL Due: Mar 7 2007, 10:00 pm...

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