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Unformatted text preview: Ch. 12: Equilibrium Equilibrium when: Remember Newtons 2 nd law: F net = F i = m a = d P dt net = i = I = d L dt P = constant L = constant 1) Linear Momentum of its center of mass is constant 2) Angular Momentum about any point is constant P = L = Static Equilibrium when: a = = d P dt = = d L dt v com = = Checkpoint 121 The fgure gives an overhead view oF a uniForm rod in static equilibrium. a) Can you fnd the magnitudes oF 1 and 2 by balancing the Forces? b) IF you wish to fnd the magnitude oF 2 by using a single equation, where should you place a rotational axis? 1) Draw a Freebody diagram showing all Forces acting on body and the points at which these Forces act. 2) Draw a convenient coordinate system and resolve Forces into components. 3) Using letters to represent unknowns, write down equations For: x =0, y =0, and z =0 4) or = 0 equation, choose any axis perpendicular to the xy plane. But choose judiciously! Pay careFul attention to determining lever arm and sign! [For xyplane, ccw is positive & cw is negative] 5) Solve equations For unknowns. Checkpoint 121 The fgure gives an overhead view oF a uniForm rod in static equilibrium. a) Can you fnd the magnitudes oF 1 and 2 by balancing the Forces? b) IF you wish to fnd the magnitude oF 2 by using a single equation, where should you place a rotational axis? Problem 127 1) Draw a freebody diagram showing all forces acting on body and the points at which these forces act. 2) Draw a convenient coordinate system and resolve forces into components. 3) Using letters to represent unknowns, write down equations for: F x =0, F y =0, and F z =0 4) For = 0 equation, choose any axis perpendicular to the xy plane. But choose judiciously! Pay careful attention to determining lever arm and sign! [for xyplane, ccw is positive & cw is negative] 5) Solve equations for unknowns. A diver of weight 580 N stands on the end of a 4.5 m diving board of negligible mass. The board is attached to two pedestals 1.5 m apart. What is the magnitude and direction of the force on the board at the left and right pedestals? Problem 127 A diver of weight 580 N stands on the end of a 4.5 m diving board of negligible mass. The board is attached to two pedestals 1.5 m apart. What is the magnitude and direction of the force on the board at the left and right pedestals? Sample Problem A uniform beam of length L and mass m is at rest with its ends on two scales. A uniform block, with mass M is rest on the beam, with its center a distance L/4 from the beams end. What do the scales read?...
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This note was uploaded on 05/20/2011 for the course PHYS 2101 taught by Professor Grouptest during the Spring '07 term at LSU.
 Spring '07
 GROUPTEST
 Angular Momentum, Center Of Mass, Mass, Momentum

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