Simple Machines

# Simple Machines

## Simple Machines

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##### Presentation Transcript

1.  Simple Machines

2. Types of Simple Machines A simple machine does work with only one movement.  Simple machines can be combined to form more complex machines We tend to think of machines as motorized devices with many moving parts.  In physics, a machine can be a simple item, like a shovel or a screw top lid

3. Overview of the 6 Simple Machines 1.  Lever  ____ 2.  Pulley  ____ 3.  Wheel & Axle ____ 4.  Inclined Plane  ____ 5.  Screw _____ 6.  Wedge ____ Match the tool... A.  Knife B.  Crowbar C.  Pencil SharpenerD.  Elevator E.  Wheelchair rampF.  Lid to a jar

4. Levers ---- A bar that is free to pivot or turn at a fixed point. --- The fixed point is called the FULCRUM --- The output force produced depends on the length of the arm

5. Types of Levers

6. 1st Class Lever Fulcrum is located between the input and output forces Examples: Crowbar Seesaw Scissors are two class 1 levers

7. 2nd Class Lever Effort and fulcrum are on opposite sides, load is between them Examples: Wheelbarrow Bottle opener

8. 3rd Class Levers Effort is applied between the fulcrum and the load Ex.  Baseball bat, tweezers, fishing pole

9. Levers (3 Classes) Which class is a: 1.  Hammer  ___ 2.  Wheelbarrow  ___ 3.  Scissors ____  4.  The claw of a hammer  ___5.  Refrigerator door ____ 6.  Shovel ____ 6.  Baseball bat ____

10. MEMORY TRICK *remember the word FLEx* 1.  F = fulcrum in the middle 2.  L  =  load is in the middle 3.  E = effort is in the middle x is just for fun

11. Ideal Mechanical Advantage of a Lever IMA = Length of the input arm           Length of the output arm What is the IMA of the lever shown below? ________ Lever Animations at  http://www.technologystudent.com/forcmom/lever1.htm If the output arm was only 15 m, what is the IMA of the lever? _____ As you shorten the output arm,the mechanical advantage is  [ increased / decreased ]

12. What is a pulley? 1.  Consists of a wheel and a rope (chain) 2.  A fixed pulley is actually a modified first class lever.  It is fixed because part of it is attached and doesn't move. Ex.  Elevators, dumb waiters, flagpoles 3.  Moveable pulleys multiply force

13. The Block and Tackle System of pulleys consisting of fixed and movable pulleys. Basically the weight of the object is spread over multiple ropes, meaning less force needs to be applied to raise it. Essentially the rope is longer, and you must pull it a longer distance to raise the object.   Work = force x distance How Stuff Works has an excellent explanation of this.

14. Multiple Pulleys Increase Mechanical Advantage By spreading the force over a greater distance (using more than one pulley) you will reduce the effort required to raise an object.  In each case, the length of the rope gets longer, and the effort required to lift the block gets smaller 1 pulley = 100 N 2 pulleys = 50 N 3 pulleys = 25 N

15. Check for Understanding 1.  Which design will give you the greatest mechanical advantage? 2.  If F1 = 100 N, what is F2?   3. Identify the movable and fixed pulleys in each design.

16. What is a Wheel and Axle? Shaft or axle attached to a larger wheel Examples:  door knobs, screwdrivers, faucet handles, pencil sharpener

17. Mechanical Advantage of Wheel and Axle IMA  = radius of wheel             radius of axle You can increase the advantage by using a larger wheel

18. Gears = multiple wheels that interlock together, one turn of a larger wheel causes the smaller wheel to turn multiple times In which figure(s) will the F rotate clockwise? _______

19. Inclined Planes - a sloping surface, such as a ramp, that reduces the amount of force required to do work Like all machines, the principle is to spread the Force out over a longer Distance. Ideal Mechanical Advantage     IMA  = length of slope               height of slope  Walking up the hill in a zigzag will require less effort than walking straight up the hill.

20. IMA  = length of slope           height of slope  Which of the following designs will produce the greater mechanical advantage?

21. http://youtu.be/suDJARX0nMA 1.  Energy and work are measured in ____________ 2.  For exertion, the greater the distance,                     the [ greater / lesser ] the force required. 3.  The "sloping flat thing" is actually the ____________________

22. 1. What is the pivot point of the teeter totter called? ________ 2. If you double the distance, you can _______ the forced needed.3.  Archimedes said: "give me a _______________ and I will move the _____________

23. 1. The lever gave Professor B a mechanical _____________ 2. Mechanical Advantage =  output divided by ___________ 3.  The inclined plane is less efficient due to the force of                                                                          _____________

24. The Screw - an inclined plane wrapped in a spiral around a post Examples: bolts, screws, lids, spiral staircase The Wedge - an inclined plane with two sides Examples:  Axes, knives, chisels

25. QUIZ TIME!

26. 1.  What type of machine is a wheelchair ramp? 2.  What type of machine is a crowbar?   3.  The fixed point for a lever to pivot is the _______. 4. If the LOAD is in the middle of a lever, it is called a   [1st, 2nd, 3rd ] class lever. 5.  What type of lever is pictured?          [ 1st, 2nd, or 3rd class ] 6.  A system of pulleys that reduces the force needed to lift an object is called a ________________________

27. 7.  Give an example of a wheel and axle: ____________ 8.  How can you increase the mechanical advantage of a wheel and axle? 9.  A ________ consists of multiple wheels that interlock 10.  What reduces the efficiency of an inclined plane? _____ 11.  A wedge is an _____________________ with two sides.