simple machines
DESCRIPTION
Simple Machines. Types of Simple Machines. A simple machine does work with only one movement. Simple machines can be combined to form more complex machines. - PowerPoint PPT PresentationTRANSCRIPT
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Simple Machines
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Types of Simple MachinesA 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
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Overview of the 6 Simple Machines1. Lever ____2. Pulley ____3. Wheel & Axle ____4. Inclined Plane ____5. Screw _____6. Wedge ____
Match the tool...
A. KnifeB. CrowbarC. Pencil SharpenerD. ElevatorE. Wheelchair rampF. Lid to a jar
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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
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Types of Levers
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1st Class LeverFulcrum is located between the input and output forces
Examples:CrowbarSeesawScissors are two class 1 levers
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2nd Class LeverEffort and fulcrum are on opposite sides, load is between them
Examples:WheelbarrowBottle opener
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3rd Class LeversEffort is applied between the fulcrum and the load
Ex. Baseball bat, tweezers, fishing pole
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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 ____
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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
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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? ________
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 ]Lever Animations at http://www.technologystudent.com/forcmom/lever1.htm
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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
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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.
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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 smaller1 pulley = 100 N2 pulleys = 50 N3 pulleys = 25 N
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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.
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What is a Wheel and Axle?Shaft or axle attached to a larger wheel
Examples: door knobs, screwdrivers, faucet handles, pencil sharpener
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Mechanical Advantage of Wheel and Axle
IMA = radius of wheel radius of axle
You can increase the advantage by using a larger wheel
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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? _______
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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.
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Which of the following designs will produce the greater mechanical advantage?
IMA = length of slope height of slope
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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 ____________________
http://youtu.be/suDJARX0nMA
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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 _____________
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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 _____________
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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 sidesExamples: Axes, knives, chisels
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QUIZ TIME!
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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 ________________________
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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.