# HW-18-solutions - pandey(sp34566 HW-18 swinney(57305 This...

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pandey (sp34566) – HW-18 – swinney – (57305) 1 This print-out should have 22 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001(part1of4)10.0points Consider the diagram shown below. 003(part3of4)10.0points What is the z component of the torque about point A?
Given r = 4 m, F = 8 N and θ = 41 o ,
004(part4of4)10.0points If the force were perpendicular to vectorr A but the answer is the same as in parts 1-3, what would its magnitude be?
A what is the x component of the torque about the point A (choice of axes: + x to the right, + y up, + z out of the page; origin at A)? In this case, vectorr A = < r A , 0 , 0 > and vector F new = < 0 , F new , 0 >, so that vector τ new = vectorr A × vector F new 005 10.0points
= ( 0 , 0 , r A F sin θ ) = ( 0 , 0 , (4 m)(8 N) sin 41 o ) = ( 0 , 0 , 20 . 9939 N · m ) 002(part2of4)10.0points What is the y component of the torque about point A? Which of the following is/are required for the angular momentum of a system to be con- stant? I. Zero net external torque II. Zero net energy transfer III. Zero net external force
Explanation: See Explanation 1. 3. I only correct
pandey (sp34566) – HW-18 – swinney – (57305) 2 4. II,III only 7. III only
006(part1of3)10.0points A mass 4 . 6 kg is attached to a light cord,
which is wound around a pulley. The pulley is a uniform solid cylinder of radius 6 . 8 cm and mass 3 . 5 kg. What is the magnitude of the net torque on the system about the point on the axis at the center of the pulley? The acceleration due to gravity is 9 . 8 m / s 2 . 007(part2of3)10.0points
When the mass has a speed v = 26 m / s, the pulley has an angular speed ω = v R . Determine the magnitude of the total an- gular momentum of the system about a point on the axis at the center of the pulley?