| Question |
Answer |
| block and tackle | An arrangement of fixed and movable pulleys connected by ropes; has a high mechanical advantage. |
| distance principle | States that any reduction in the effort force that is required will be paid for by an increased distance through which that force must act. |
| efficiency | The percent of the work input returned as useful output. |
| effort | The force that must be applied to a simple machine to make it produce work. |
| effort arm | The distance from the fulcrum to the effort. |
| first-class lever | A lever in which the fulcrum is located between the effort and the resistance. |
| fulcrum | The fixed point about which a lever turns. |
| inclined plane | A slanted surface used to raise objects. |
| joule(j) | The SI unit of energy; equal to 1 Newton-meter of work. |
| law of moments | The method of computing the amount of force exerted by levers with unequal arms; w1d1 = w2d2. |
| lever | A rigid bar capable of turning about a fulcrum. |
| mechanical advantage (M.A.) | The amount by which a machine magnifies effort (force). |
| pitch | The distance between two adjacent threads on a screw; how high or low a tone sounds to an observer (related to frequency). |
| power (P) | The amount of work done in a given period of time. P = W/t. |
| pulley | A modified lever consisting of a rope that moves around a grooved wheel; can be movable or fixed. |
| resistance | The force against which a simple machine works; opposition to the flow of electrons. |
| resistance arm | The distance from the fulcrum to the resistance. |
| scientific idealization | Approximating an answer when an extremely accurate one is not needed. |
| screw | An inclined plane wound around a cylinder or cone. |
| second-class lever | A lever in which the resistance is located between the fulcrum and the effort. |
| simple machines | One- or two- part devices that make work easier; lever, wheel and axle, pulley, inclined plane, wedge, screw. |
| third-class lever | A lever in which the effort is applied between the fulcrum and the resistance. |
| torque | This is the product of a force and the length of the lever arm from the pivot point. |
| watt (W) | The SI unit of power; 1 joule of energy per second. |
| wedge | Two inclined planes placed back to back. |
| wheel and axle | Modified lever in which the effort arm and the resistance arm revolve around a central fulcrum. |
| work | The product of the force applied on an object multiplied by the distance the object moved; W = Fd |
Ch.18 LTI-MA 509
