Mechanical advantage

In physicsengineering mechanical advantage (MA) isfactor by whichmachine multipliesforce put into it. The mechanical advantage can be calculated forfollowing simple machines by usingfollowing formulas:

• Lever: MA = lengtheffort arm ÷ lengthresistance arm.

• WheelAxle: A wheelessentiallyleverone armdistance betweenaxle andouter point ofwheel, andotherradius ofaxle. Typically this isfairly large difference, leadingan equally large mechanical advantage. Thiswhy even simple wheelswooden axles runningwooden blocks will still turn freely, becausefrictionoverwhelmed byrotational force ofwheel multiplied bymechanical advantage.

• Pulley: Pulleyswheels thatconnected togetherropes. In doing sodirection offorce onrope can be changed,little lossforce duefriction (forsame reasons aswheel). However pulleys can be "added together"create additional mechanical advantage by havingrope looped over several pulleysturn. A pulleyone rope (single fixed pulley) has an MA = 1, that is, no advantage (or disadvantage). A pulleytwo ropes (single moveable pulley) hasMA = 2. A pulley6 ropes (blocktackle) hasMA = 6.

• Inclined Plane: MA = lengthslope ÷ heightslope

Most generally,mechanical advantagecalculated thus:

• MA = (the distance over which forceapplied) ÷ (the distance over whichloadmoved)

also,Force exerted IN tomachine ×distance moved IN will always be equal toforce exerted OUT ofmachine ×distance moved OUT. For example; usingblocktackle6 ropes, and600 pound load,operator would be requiredpullrope 6 feet,exert 100 poundsforceliftload 1 foot, therefore:

• (force100 × distance6) = (force out 600 × distance out 1)

or more basic, WORK_in = WORK_out

This requires an ideal simple machine, meaning that thereno losses duefriction or elasticity. If friction or elasticity exist insystem efficiency will be lower; Work_in will be greater than Work_out

Mechanical advantage also appliestorque. A simple gearsetablemultiply torque.

Theretwo typesmechanical advantage:

1. Ideal mechanical advantage (IMA)
2. Actual mechanical advantage (AMA)