Chapter 13 Key Terms:
| balance | ability to control equilibrium |
| base of support | area bound by the outermost regions of contact between a body and support surface or surfaces |
| center of mass, mass centroid, center of gravity | the point around which the mass and weight of a body are balanced in all directions |
| coefficient of friction | number that serves as an index of the interaction between two surfaces in contact |
| coefficient of restitution | number that serves as an index of elasticity for colliding bodies |
| couple | pair of equal, oppositely directed forces that act on opposite sides of an axis of rotation to produce torque |
| dynamic equilibrium (D'Alembert's principle) | concept indicating a balance between applied forces and inertial forces for a body in motion |
| first class lever | lever positioned with the applied force and the resistance on opposite sides of the axis of rotation |
| friction | force acting at the area of contact between two surfaces in the direction opposite that of motion or motion tendency |
| fulcrum | point of support or axis about which a lever may be made to rotate |
| impact | collision characterized by the exchange of a large force during a small time interval |
| impulse | product of a force and the time interval over which the force acts |
| kinetic energy | capacity to do work by virtue of a body's motion |
| kinetic friction | constant magnitude friction generated between two surfaces in contact during motion |
| lever | simple machine consisting of a relatively rigid barlike body that may be made to rotate about an axis |
| linear momentum | quantity of motion, measured as the product of a body's mass and its velocity |
| maximum static friction | maximum amount of friction that can be generated between two static surfaces |
| mechanical advantage | ratio of force arm/resistance arm for a given lever |
| moment arm | shortest (perpendicular) distance between a force's line of action and an axis of rotation |
| normal reaction force | force acting perpendicular to two surfaces in contact |
| perfectly elastic impact | impact during which the velocity of the system is conserved |
| perfectly plastic impact | impact resulting in the total loss of system velocity |
| potential energy | capacity to do work by virtue of a body's position, calculated as the product of weight and height |
| power | rate of work production that is calculated as work divided by the time during which the work was done |
| reaction board | specially constructed board for determining the center of gravity location of a body positioned on top of it |
| second class lever | lever positioned with the resistance between the applied force and the fulcrum |
| segmental method | procedure for determining total body center of mass location based on the masses and center of mass locations of the individual body segments |
| stability | resistance to disruption of equilibrium |
| static equilibrium | motionless state characterized by S Fv = 0, S F h = 0, and S T = 0 |
| strain energy | capacity to do work by virtue of a deformed body returning to its original shape |
| third class lever | lever positioned with the applied force between the fulcrum and the resistance |
| torque | the rotary effect of a force about an axis of rotation, measured as the product of the force and the perpendicular distance between the force's line of action and an axis of rotation |
| work | expression of mechanical energy that is calculated as force multiplied by the displacement of the resistance in the direction of the force |