chap 9

• center of gravity the point where the total weight of the body is assumed to be concentrated
• dynamic equilibrium a state of equilibrium in which the net external force and torque on a system moving with constant velocity are zero
• mechanical advantage the ratio of output to input forces for any simple machine
• neutral equilibrium a state of equilibrium that is independent of a system’s displacements from its original position
• stable equilibrium a system, when displaced, experiences a net force or torque in a direction opposite to the direction of the displacement
• perpendicular lever arm the shortest distance from the pivot point to the line along which lies
• static equilibrium a state of equilibrium in which the net external force and torque acting on a system is zero
• SI units of torque newton times meters, usually written as N·m
• static equilibrium equilibrium in which the acceleration of the system is zero and accelerated rotation does not occur
• torque turning or twisting effectiveness of a force
• unstable equilibrium a system, when displaced, experiences a net force or torque in the same direction as the displacement from equilibrium
• moment of inertia rotational analogue of mass; measures an object's resistance to change in angular motion
• momentum mass times velocity