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The Greek letter Tau. The Physical Study of Balance. Equilibrium. Conditions for equilibrium. Sum of forces is zero Tendency to rotate is zero. Torque. the effectiveness of a force in causing rotation on a rigid object also called moment of force. Rigid Object vs. Point/Particle Model.
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The Physical Study of Balance Equilibrium
Conditions for equilibrium Sum of forces is zero Tendency to rotate is zero
Torque the effectiveness of a force in causing rotation on a rigid object also called moment of force
Prerequisite Observation for 2nd Condition • Which of the following forces will effectively rotate the beam at point O?
Prerequisite Observation for 2nd Condition • Which of the following forces will effectively rotate the beam at point O?
Prerequisite Observation for 2nd Condition • Which of the following forces will effectively rotate the beam at point O?
Prerequisite Observation for 2nd Condition • Which of the following forces will effectively rotate the beam at point O?
Factors that determine torque • The amount of force perpendicular to the lever arm. • The distance of the force from the pivot point.
Guidelines for Problem Solving • Illustrate all the forces and the lever arm for each. • Torque is the product of force and its distance from the point of rotation. • Force and the lever arm must always be perpendicular. • Establish the point of rotation. • Equate the sum of forces to zero. • Equate the sum of torques to zero.
Exercise A 50.0 N uniform beam, 10.0 m in length, is suspended on a support as shown. If the fulcrum divides the beam into the ratio of 2:3, where should a 6.00 kg object be placed to balance the beam? x
Exercise • In a Singkil dance, two men are carrying a princess on a bamboo pole that is 5.00 m long and weighs 200.0 N. If the princess weighs 425 N and sits 1.50 m from one end, how much weight must each man support?
Exercise • (Follow up) • Where should the princess sit so that one man supports her with a force twice that of the other? ?
Exercises • Consult page 117 of your book and read Practice Exercise 5.8
Rx lRx 3.5m w Ry f 1m lw
Exercises A uniform 50.0 N ladder rests on a frictionless wall as shown. What minimum coefficient of friction is needed on the ground to prevent it from slipping? 5m 2m
Exercises A uniform aluminum beam 9.00 m long, weighing 300 N, rests symmetrically on two supports 5.00 m apart. A boy weighing 600 N starts at point A and walks toward the right. • From your diagram, how far beyond point B can the boy walk before the beam tips?