Topic 4 Chapter 3 Equilibrium of a Particle 2D A spool of given weight W is suspended from a crane When designing the spreader bar we need to know the cable forces AB and AC to make sure the rigging doesn t fail Equilibrium of a Particle Newton s 1st law governs statics Resultant of forces in Cartesian coordinate system Steps to solve Equilibrium Problems Draw Free Body Diagram Apply Equilibrium Conditions Notes about forces Gravity W place at center of gravity of body Contact forces forces that arise between bodies that physically touch They are perpendicular to contact surfaces Notes about forces cont Flexible rope or cables always in tension Spring Forces length of spring changes in proportional to the force acting on it What Why and How of a Free Body Diagram Free Body Diagrams FBD are one of the most important things for you to know how to draw and use What It is a drawing that shows all external forces acting on the body Why It is essential for writing the equations of equilibrium used to solve for unknowns usually forces or angles A B C 100 lb How Steps 1 Decide on body or bodies to isolate 2 Draw outline of isolated body free of surroundings 3 Draw all forces applied by other bodies Active forces want to move body Reactive forces tend to resist motion Show all known and unknown forces magnitudes and directions 4 Indicate set of coordinate axes on FBD The sphere has a mass of 6 kg and is supported as shown Draw FBD of sphere Draw FBD of cord CE Draw FBD of knot at point C Draw a FBD for use when solving for the cable forces when the system is in equilibrium The sphere has a mass of 6 kg and is supported as shown Determine the force in the spring and in the cable ABC Determine the forces in cables AB and AD when the system is in equilibrium Determine the unstretched length of DBto hold the 40 kg crate in the position shown Take k 180 N m Determine the tension in the cables AB BC and CD necessary to support the 10 kg light at B and the 15 kg light at C Also find the angle Determine the maximum weight W of bucket F that can be supported in the position shown if each cable can support a maximum tension of 600 N before it fails Items to complete Submit the classwork ICW 3 6 8 to the submission box on Canvas by midnight Thursday 6 9 Complete Homework 4a in Pearson by midnight Thursday 6 9 Scan and upload a pdf of your FBD s needed for Homework 4 called Hwk 4b Paper with FBD s for 2D particle equilibrium in Canvas by midnight Thursday 6 9 Read the MEEN 221 Quiz Instructions with Honorlock before class on Friday 6 10