Machine notes CP Physics Ms. Morrison

Machines Devices that make work easier to do (transfer energy) Two ways make work easier: Machines change the direction of your force. (ex. Pulleys) Machines multiply the force you apply to it. Note: You do the work on the machine and then the machine does work on the object.

Simple Machines Six Simple Machines Levers Pulleys Wheel and axles Inclined Planes Wedges Screws

Levers Long rigid bar with a support called a fulcrum Examples: crowbars, car jacks

Pulleys Special type of lever Has grooved wheel over which a rope passes Can have a single pulley or combinations of pulleys Examples: window shade pulls, block and tackle, well, flag poles

Wheel and axle Special type of lever Consists of a wheel attached to an axle Examples: pencil sharpener, egg beater

Inclined plane Flat surface with one end higher than the other Examples: moving ramps, wheelchair ramps

Wedge Inclined plane with either one or two sloping sides Examples: door stops, knives, axes, scissors, chisels

Screw An inclined plane which is spiral, you move the plane rather than the load Examples: wood screws

Mechanical advantage Indicates how much the machine multiplies your force Equation: MA = Fr/Fe MA = mechanical advantage (no unit) Fr = resistance force (equals weight of the object) Fe = effort force (force you apply to the machine)

Ideal mechanical advantage Second form of mechanical advantage Based on an ideal machine which transfers 100% of your energy Equation: IMA = de/dr IMA = ideal mechanical advantage de = effort distance (distance you apply force) dr = resistance distance (distance machines moves)

Efficiency Shows how much of the work you put into the machine (input work) is actually used to do work on the object by the machine (output work) Equation: Efficiency = Wo/Wi x 100% Wo = output work (J) Wi = input work (J) Machines cannot multiply your work or energy – they can only multiply force MACHINES CANNOT DO MORE WORK THAN THE WORK YOU PUT INTO THEM