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Unformatted text preview: homework 09 RAHMAN, TARIQUE Due: Feb 25 2008, 3:00 am 1 Question 1, chap 6, sect 1. part 1 of 1 10 points In order to slide a heavy desk across the floor at constant speed in a straight line, you have to exert a horizontal force of 500 New- tons. Compare the 500-Newton horizontal push- ing force F to the frictional force f between the desk and the ground. 1. F > f ; the frictional force is always less than any other force acting on the object. 2. It depends on which direction the desk is moving. 3. F = f from Newtons first law. 4. F = f from Newtons third law. 5. F < f ; the frictional force is greater than the pushing force since it is such a heavy desk. Question 2, chap 6, sect 1. part 1 of 1 10 points When an object is moving in the air, the air drag force is in the opposite direction to the velocity. Consider a light foam ball that is thrown up into the air. When is the net force on the ball greatest? 1. When the ball moves down 2. When the ball is at the top of its trajec- tory 3. When the ball moves up 4. The net force is constant. Question 3, chap 6, sect 1. part 1 of 1 10 points The force F exerted on the block pushes the block against the ceiling and at the same time accelerates the block to the right. m F a Find the kinetic friction between the block and the ceiling. 1. f k = ( F sin - mg ) 2. f k = ( F sin + mg ) 3. f k = F sin 4. f k = mg Question 4, chap 6, sect 1. part 1 of 3 10 points Consider a force pulling 3 blocks along a rough horizontal surface, where the masses are a multiple of a given mass m , as shown in the figure below. The coefficient of the kinetic friction is...
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