# HW_11 - P112 Spring 2007 Homework#11 Due Friday April 13th...

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P112 Spring 2007 Homework #11 Due: Friday April 13th, 2007 – At lecture Reading: 11.1-11.3, 10.4-10.7 Not all concepts will be covered in class – you are responsible for all material in the reading and in the homework problems. Warm-up Exercises: (Answer only will be marked) 1. A solid wood door 1.00 m wide and 2.00 m high is hinged along one side and has a total mass 40.0 kg. Initially open and at rest, the door is struck at its center by a handful of sticky mud with mass 0.500 kg, traveling perpendicular to the door at 12.0 m/s just before impact. Find the angular speed of the door. Does the mud make a significant contribution to the moment of inertia? 2. See Figure 11.43 in your Text Book. A gate 4.00 m wide and 2.00 m high weighs 500 N. Its center of gravity is at its center, and it is hinged at A and B. To relieve the strain on the top hinge, a wire is connected from C to D, as shown in the Figure. The tension in CD is increased until the horizontal force at hinge A is zero. a) what is the tension in the wire CD? b) what is the magnitude of the horizontal component of the force at hinge B? c) what is the combined vertical force exerted by hinges A and B? Mathematics Exercises: 3. Find a vector which is perpendicular to both u=(3,0,2) and v=(1,1,1) Estimation: (Marked based solely on logic) 4. Estimate the tension in the metal suspension rods of the Golden Gate Bridge in San Francisco. Problems: 5. A ladder 5.0 m long rests against a frictionless vertical wall with its lower end 3.0 m from the wall. The ladder weighs 160 N. The coefficient of static friction between the foot of the ladder and the ground is 0.40. A man weighing 740 N climbs slowly up the ladder. a) What is the maximum frictional force that the

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## This note was uploaded on 03/27/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Spring '07 term at Cornell.

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HW_11 - P112 Spring 2007 Homework#11 Due Friday April 13th...

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