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BRMS 6 th Science Mrs. Bright

BRMS 6 th Science Mrs. Bright. Standard 6-5.7; 6-5.8. Explain how the design of simple machines helps reduce the amount of force required to do work. Illustrate the ways that simple machines exist in common tools and in complex machines. 1. What is a Simple Machine?.

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BRMS 6 th Science Mrs. Bright

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  1. BRMS 6th Science Mrs. Bright

  2. Standard 6-5.7; 6-5.8 • Explain how the design of simple machines helps reduce the amount of force required to do work. • Illustrate the ways that simple machines exist in common tools and in complex machines.

  3. 1. What is a Simple Machine? • A. It does the work with only one movement. • B. It is a device that makes work easier. • C. It reduces the amount of force required to do work.

  4. 2. How do simple machines make work easier? • Machines • A. Change the amount of force you exert • B. Change the distance over which you exert force • C. Change the direction in which you exert force • D. Do change the amount of work done NOT

  5. 3. Work ‘input’ and ‘output’ A. Work INPUT is the amount of work done ON a machine. B. Work OUTPUT is the amount of work done BY a machine. C. The output always EQUALS the input. Wout = Win Fout x Dout = Fin x Din 10N x 3m = 2N x 15m 30 = 30 15 m Din Dout 3 m 2 N 10 N

  6. 4. List the 6 simple machines. Lever Inclined Plane Pulley Wheel and Axle Wedge Screw

  7. INCLINED PLANE • 1. A flat, sloping surface that reduces the amount of force required to lift an object.

  8. The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

  9. 2. As the incline plane becomes longer, the force needed to move the object becomes smaller. 3. Decreasing the height of the inclined plane also reduces the force How is an inclined plane useful?

  10. Incline Plane Examples • 4. Ramp • Slide • Stairs • Ladder

  11. WEDGES • 1.Two inclined planes joined back to back. • 2. An incline plane that moves. • 3. Wedges are used to split things.

  12. How are wedges useful? • 4.You need less force as the wedge becomes longer & thinner.

  13. Wedge Examples • 5. scissors • knife blade • nails • teeth • door stop • axe

  14. SCREWS • 1.A screw is an inclined plane wrapped around a post or cylinder.

  15. Screws

  16. How are screws useful? • 2.You need less force to fasten objects together as the number of threads in the screw increase.

  17. Screw examples • 3. Light bulb • Bottle cap • Screw • Bolts • Jar lids

  18. LEVER • 1. A lever is a rigid bar or board that is free to move around a fixed point called a fulcrum. • 2. There are 3 classes of levers.

  19. Levers-First Class • 1. E-F-L • 2. The fulcrum is in the middle and the load (output force) and effort (input force) is on either side

  20. First Class Lever Examples . 3. Crowbars, scissors, pliers, tin snips and seesaws.

  21. Levers-Second Class • 1. E-L-F • 2. The load (output force) is in the middle.

  22. Second Class Lever Examples 3. Nut crackers, wheel barrows, doors, and bottle openers.

  23. Levers-Third Class • 1. L-E-F • 2. The effort (input force) is in the middle.

  24. Third Class Lever Examples 3.Tweezers, arm, hammer, shovel, baseball bat

  25. WHEEL & AXLE ●1. Made from 2 circular objects of different sizes that are attached & rotate together. • 2.The larger object is the wheel & the smaller object is the axle inserted through the middle of the wheel.

  26. Wheel & Axle Examples 3. Fan, ferris wheel, bicycle wheels, door knobs, steering wheels, screwdrivers, & gears. • The axle is stuck rigidly to a large wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin.

  27. GEARS-Wheel and Axel Each gear in a series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

  28. PULLEY • 1.A pulley has a grooved wheel with a rope, chain, or belt running along the groove.

  29. Diagrams of Pulleys Fixed pulley: 1.Attached to a structure & changes only the direction of the force. 2. EXAMPLE: flagpole, window blind 1. Reduce the effort force & are NOT attached to a structure. 2. EXAMPLE: construction crane Movable Pulley:

  30. No Mechanical Advantage in a Fixed Pulley ●The only thing that changes is the direction of the force you have to apply to lift the weight. ● You still have to apply 100 pounds of force to keep the weight suspended, and you still have to reel in 100 feet of rope in order to lift the weight 100 feet. ●If you are going to suspend the weight in the air, then you have to apply an upward force of 100 pounds to the rope. ● If the rope is 100 feet long and you want to lift the weight up 100 feet, you have to pull in 100 feet of rope to do it..

  31. ●If you want to lift the weight 100 feet higher, then you have to reel in twice as much rope 0- 200 feet of rope must be pulled in. ● This demonstrates a force-distance tradeoff. The force has been cut in half but the distance the rope must be pulled has doubled. ●You can see that the weight is now suspended by two pulleys rather than one. ●The weight is split equally between the two pulleys, so each one holds only half the weight, or 50 pounds.

  32. Combined Pulley The effort needed to lift the load is less than half the weight of the load. The main disadvantage is it travels a very long distance.

  33. The 6 Simple Machines Screw Wedge Inclined Plane Pulley Wheel and Axle Lever

  34. What Simple Machine is Missing?

  35. Correct!!! The Wheel and Axle

  36. Name the Simple Machines

  37. Lever • Wheel and Axle • Inclined Plane • Lever • Wedge • Inclined Plane

  38. Compound Machines • 1.Simple Machines can be put together in different ways to make complex machinery • 2.EXAMPLES: • Scissors: 2 levers & 2 wedges • Fishing pole: a lever, a wheel & axle, a pulley • Bicycle: levers, wheel & axle, screws

  39. Rube Goldberg Machines Rube Goldberg machines are examples of complex machines. All complex machines are made up of combinations of simple machines. Rube Goldberg machines are usually a complicated combination of simple machines. By studying the components of Rube Goldberg machines, we learn more about simple machines

  40. Safety Device for Walking on Icy Pavements When you slip on ice, your foot kicks paddle (A), lowering finger (B), snapping turtle (C) extends neck to bite finger, opening ice tongs (D) and dropping pillow (E), thus allowing you to fall on something soft.

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