5 6 Translate/ Direction System FBD Variable Rotate (unit vector) S of S About point MG road-map equation Additional unknowns* Unknown scalar variable (e.g., a position, velocity, force, or torque variable). Type of motion associated with the variable: translate or rotate. Col. Enter the following information 1 2 3 4 Vector direction (e.g., unit vector i) associated with the direction of motion. List of objects whose motion (e.g., velocity or angular velocity) is directly affected by the variable in column 1 ("freeze" any variable other than the variable in column 1 and decide what objects must move). This picks a system S that reduces/eliminates constraint forces. Note: If the variable in column 1 is a force measure, treat it as a velocity measure and determine what objects move. If it is a torque measure, treat it as an angular velocity measure and determine what objects move. Draw FRD here 5 Draw a free-body diagram of system S (draw relevant contact/distance forces). Note: See force/torque models for gravity, springs, dampers, air-resistance, etc., in Chapter 21. 6 Point O about which moments are to be taken (applicable if column 2 is rotate). Note: Choose point O to eliminate moments of unknown forces (e.g., contact forces on S)-look at the FBD. 7a If column 2 was translate (N is a Newtonian reference frame), use: or D To calculate m Nam for a system S of objects A, B, C: 7b If column 2 was rotate, use: (13.3) or 5/0 0 Statics For a system S with a particle Q and rigid body B: For particle Q N 0x m NA8/0 NB/O (10.3) = For rigid body B B/O NB/B +0xm N (15.3) B/B. NaCe