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Unformatted text preview: homework 08 BAUTISTA, ALDO Due: Feb 8 2006, 4:00 am 1 Version number encoded for clicker entry: V1:1, V2:4, V3:2, V4:4, V5:3. Question 1 Part 1 of 2. 10 points. Three objects can only move along a straight, level path. The graphs below show the position d of each of the objects plotted as a function of time t . d t I d t II d t III The magnitude of the velocity k ~v k of the object increases in which of the cases? 1. I, II, and III 2. II and III only 3. III only correct 4. I and III only 5. I only 6. I and II only 7. II only Explanation: Case I: The object moves at constant speed. Case II: The object remains at rest. Case III: The speed of the object increases with time; i.e. , constant acceleration. Thus, the magnitude of the velocity of the object increases only in case III. Question 2 Part 2 of 2. 10 points. The sum of the forces X F i = 0 on the object is zero in which of the cases? 1. I and II only correct 2. I only 3. III only 4. I, II, and III 5. II and III only 6. II only 7. I and III only Explanation: When the sum of forces on the object is zero, the acceleration of object is zero by Newtons 2nd law. In cases I and II, the velocity of the object doesnt change with the time, so the sum of the forces on the object is zero. In case III, the object is accelerating, so the sum of forces on the object is not zero. Question 3 Part 1 of 1. 10 points. A block of mass m accelerates with acceler- ation g up a frictionless plane that is inclined at an angle above the horizontal. The force F o that pushes the block is at an angle above the horizontal. Find the force F o . m F o 1. m g 1 + sin cos( - ) 2. m g 1 cos( + ) 3. m g 1- sin cos( - ) 4. m g 1- sin cos( + ) homework 08 BAUTISTA, ALDO Due: Feb 8 2006, 4:00 am 2 5. m g 1 + sin cos( - ) 6. m g 1 + sin cos( + ) correct 7. m g 1 + sin cos( - ) 8. m g 1 + sin cos( + ) 9. m g sin cos( + ) 10. m g 1 + sin cos( - ) Explanation: The acceleration up the plane is given, a = g . The angle that F o makes with respect to the inclined plane is + . So the component of F o which is parallel to the inclined plane is...
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This note was uploaded on 10/13/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
- Spring '08