Chapter 13 Skill Building

Chapter 13 Skill Building - MasteringPhysics: Assignment...

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MasteringPhysics: Assignment Print View PSS 13.1: Let's Go for a Spin Learning Goal: To practice Problem-Solving Strategy 13.1 for problems involving rotational dynamics. A uniform board of mass and length is pivoted on one end and is supported in the horizontal position by a rope attached to the other end. Another rope, attached to the board a distance from the pivot point, is being pulled straight down with a constant force of magnitude . Suddenly, the rope attached to the end of the board breaks. What is the instantaneous angular acceleration of the board? MODEL: Model the object as a simple shape. VISUALIZE: Draw a pictorial representation to clarify the situation, define cordinates and symbols, and list known information. Identify the axis about which the object rotates. Identify forces and determine their distance from the axis. For most problems it will be useful to draw a free-body diagram. Identify any torques caused by the forces and the signs of the torques. SOLVE: The mathematical representation is based on Newton's 2nd law for rotational motion: . Find the moment of inertia in Table 13.13 or, if needed, calculate it as an integral or by using the Parallel-Axis Theorem. Use rotational kinematics to find angles and angular velocities. ASSESS: Check that your result has the correct units, is reasonable, and answers the question. Identify the object for which you will write the equation of Newton's 2nd law. Make reasonable simplifying assumptions. Part A
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MasteringPhysics: Assignment Print View The board should be modeled as ANSWER: a thin rod in rotational equilibrium. a thin rod in total equilibrium. a thin rod rotating about its center. a thin rod rotating about one end. Draw the pictorial representation and list all known information. Mark all forces. Identify the axis of rotation and show the distances from that axis to each force applied. Use your sketch to answer the following questions. Part B How far is the axis of rotation from the center of mass of the board? Express your answer in terms of quantities given in the problem introduction. ANSWER: Part C How far is the axis of rotation from the point of application of force ? Express your answer in terms of quantities given in the problem introduction. ANSWER: Part D How many forces are acting on the board after the rope attached to the end of the board breaks? ANSWER: one two three four Part E
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MasteringPhysics: Assignment Print View When you write Newton's 2nd law for the rotational motion of the board, how many nonzero torques will it contain? ANSWER: one two three four Although the reaction force acting on the board at the pivot point is not zero, its torque about that point is zero because that force is applied at the axis of rotation, and the moment arm is zero.
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Chapter 13 Skill Building - MasteringPhysics: Assignment...

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