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Machines

Machines. Making Work Easier. Machines. A device that makes work easier Some powered by engines/motors, others powered by people What are some examples?. Machines. Simple Machine = a device that does work with only one movement 6 types. Advantages of Machines. They make work easier by…

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Machines

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  1. Machines Making Work Easier

  2. Machines • A device that makes work easier • Some powered by engines/motors, others powered by people • What are some examples?

  3. Machines • Simple Machine = a device that does work with only one movement • 6 types

  4. Advantages of Machines • They make work easier by… • Multiplying the effort force • Changing the direction of the applied force you exert • Increasing the distance through which the resistance force moves • Overcoming gravity and friction

  5. Applying Force and Doing Work • Effort Force = the force applied to a machine • Resistance Force = the force applied by the machine to overcome resistance

  6. Review • Where is the effort force? • Where is the resistance force? C B A

  7. Applying Force and Doing Work • W = Fd (Work = Force x distance) • Measured in Joules (J) • You push a box with a force of 200 N. The box moves 1 m. How much work did you do? • W = 200 N x 1 m • W = 200 J

  8. Applying Force and Doing Work • A girl lifts a 12N weight 1.5 m. How much work does she do on the weight? • F = • d = • W = Fd

  9. Applying Force and Doing Work • Remember, energy is always conserved so… • You never get more work out than you put in • Win = Wout (in an ideal machine) • Why will work out always be smaller?

  10. The Simple Machines

  11. Levers • A bar that is free to pivot, or turn, about a fixed point • Fulcrum = the fixed point of a lever • Effort Arm = the part of the lever on which the effort force is applied • Resistance Arm = the part of the lever that exerts the resistance force

  12. Levers • Teeter-totters, can openers, tennis rackets • Helps you do more work with the strength you already have

  13. 3 Types of Levers • First Class = fulcrum is between the effort and resistance forces (teeter-totter) • Multiplies the effort force and changes its direction • Effort moves farther than Resistance

  14. 1st Class Lever • When the fulcrum is closer to the effort than to the load: • There is a loss in force • There is a gain in speed and distance

  15. 1st Class Lever • When the fulcrum is closer to the load than to the effort: • There is a loss in speed and distance • There is a gain in force.

  16. 1st Class Lever • When the fulcrum is midway between the effort and the load: • There is no change in force, speed, or distance

  17. 3 Types of Levers • Second Class = resistance is located between the effort force and the fulcrum (wheelbarrow) • Always multiplies effort force • Effort moves farther than Resistance

  18. 3 Types of Levers • Third Class = effort force is located between the resistance force and the fulcrum (fishing pole) • Increases speed (cannot multiply the force) • Resistance moves farther than Effort • Multiplies the distance the effort force travels

  19. How well do you know your levers? • 1st class B. 2nd class C. 3rd class

  20. Pulleys • A grooved wheel with a rope, chain, or belt running along the groove • Examples: Flagpole, blinds • The two sides of the pulley are the effort arm and resistance arm • What does a pulley do? • Changes the direction of the force • Makes it easier to lift things to high-rise areas

  21. 3 Types of Pulleys • A fixed pulley is attached to something that does not move. • Changes the direction of the effort force. • Disadvantage: to have to apply more effort than the load

  22. 3 Types of Pulleys • A movable pulley moves with the load • May be attached to a construction crane • Does multiply the effort force • Cannot change the direction of the effort force

  23. Movable Pulley • Disadvantage: have to pull or push the pulley up or down • Advantage: Less effort to pull the load

  24. 3 Types of Pulleys • Block and Tackle Pulley = a movable pulley and a fixed pulley • The effort needed to lift the load is less than half the weight of the load

  25. Block and Tackle Pulley • Advantage: effort is less than half of the load • Disadvantage: travels a very long distance

  26. Wheel and Axle • A lever that rotates in a circle around an axle • Two wheels of different sizes connected – the axle being the smaller wheel • Larger wheel may be a crank handle or faucet handle • Examples: door knob water faucet

  27. Wheel and Axle • A gear is a wheel with teeth along its circumference • Effort is exerted on one gear to cause the other gear to turn

  28. Inclined Plane • A plane is a flat surface • Inclined plane is a plane that is slanted • Example: Ramp • Used to move things from a lower to a higher place or vice versa

  29. Inclined Plane How does the amount of work done with a ramp compare to the amount of work done lifting the object? • Work will be the same • Force to lift would be greater than the force used to push • Distance pushed up the ramp would be farther than the distance lifted • Not less work, but less effort

  30. Screw • An inclined plane wrapped around a cylinder • Multiplies an effort force by acting through a long effort distance • The closer the threads on a screw, the greater the mechanical advantage • The plan actually slides through the wood

  31. Wedge • An inclined plane with one or two sloping sides that moves • The wedge is used to increase force • The material remains in place while the wedge moves through it • A wedge changes the direction of the input force

  32. Wedge • Examples: ax, knife, chisel • The “sharper” the wedge, the greater the mechanical advantage • Can be used to split, cut, or fasten (nail/doorstop)

  33. Compound Machines • A combination of two or more simple machines • Examples: • Lawn mower • Pencil sharpener • Ax • Bicycle

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