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P. Sci.

P. Sci. Unit 3 Machines. Machine – a device that makes doing work easier by…. increasing the force that can be applied to an object. (car jack). increasing the distance over which the force can be applied. (ramp). by changing the direction of the applied force. (opening the blinds).

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P. Sci.

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  1. P. Sci. Unit 3 Machines

  2. Machine – a device that makes doing work easier by…

  3. increasing the force that can be applied to an object. (car jack)

  4. increasing the distance over which the force can be applied. (ramp)

  5. by changing the direction of the applied force. (opening the blinds)

  6. Work In Effort force – FE(Force in) The force applied to the machine (usually by you) Work in – Win(Force in x distance in) The work done by you on the machine

  7. Work Out Resistance force – FR(Force out) The force applied by the machine to overcome resistance Work out – Wout (Force out x distance out) The work done by the machine

  8. Ideal machine Win = Wout 100% energy transfer. There is no such thing as an ideal machine – you always lose some energy (through friction, air resistance, etc.)

  9. Efficiency – a measure of how much of the work put into a machine is changed into useful output work by the machine. (less heat from friction)

  10. efficiency = (Wout / Win ) x 100% Win is always greater than Wout

  11. Mechanical Advantage • How much a machine multiplies force or distance output force (FR) • MA = input force (FE) Or input distance output distance

  12. Lever MA = Length of effort arm Length of resistance arm Remember that Length is the same as distance or LE LR

  13. Inclined Plane MA = effort distance Resistance distance or length of slope or l height of slope h

  14. Pulley • The MA of a pulley or pulley system is equal to the number of pulleys supporting the load being lifted. • A single fixed pulley only changes the direction so MA = 1

  15. The End

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