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Modern Technology uses Compound Machines

Modern Technology uses Compound Machines. What simple machines do you recognize in a tow truck? A machine that is made up of two or more simple machines is a compound machine. How are simple machines related to compound machines?. Gears. Gears are based on the wheel and axle.

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Modern Technology uses Compound Machines

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  1. Modern Technology uses Compound Machines What simple machines do you recognize in a tow truck? A machine that is made up of two or more simple machines is a compound machine. How are simple machines related to compound machines?

  2. Gears • Gears are based on the wheel and axle. • The gear that turns another gear applies the input force and the gear that is turned applies the output force.

  3. Mechanical Advantage of Compound Machines • The mechanical advantage of any compound machine is equal to the product of the mechanical advantage of all the simple machines that make up the compound machine. • For example , the ideal machine advantage of a pair of scissors would be the product of the ideal mechanical advantage of its two levers and two wedges.

  4. Compound Machines and Friction • Compound machines typically must overcome more friction than simple machines, because they have more moving parts. • Scissors for example have a lower efficiency than one lever because they have more moving parts.

  5. Mechanical Advantage • When a machine helps you work, there is an advantage to them. The number of times a machine multiples the input force is called the machine’s mechanical advantage. • To find a machine’s mechanical advantage, divide the output force by the input force. • Mechanical advantage= Output force/Input force

  6. Mechanical advantage of a machine • For machines such as a rake the output force is less than the input force. • If the input force of the rake is 10 newtons and the output force is 5 Newtons mechanical advantage is .5 Input force Output force

  7. Output Work is always less than input work • The work you do on a machine is called the input work, and the work the machine does in turn is called the output work. • A machines efficiency is the ratio of its output work to the input work. • An ideal machine would be 100 % efficient. • Actual machines lose input work to friction.

  8. Calculating Efficiency • You can calculate a machines efficiency by dividing the machines output work by it’s input work and multiplying that number by 100. • Efficiency (%) =Output work/Input work x 100

  9. Calculating Efficiency • Work is measure in Joules, suppose you do 600 J of work using a rope system to lift a box. The work done is 540J. • Efficiency= 540 J/600 J x 100=90%

  10. Increasing Efficiency • All machines lose input force to friction, one way to improve efficiency is by reducing friction. • Oil is used to reduce friction between the moving parts of a car engine and a bicycle.

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