1. Simple Machines
V205.07

2. Simple Machines
Devices such as levers, ramps, and pulleys that make our work easier. 
They allow us to apply effort at one place to do work at another point and/or to change the direction of a force.   

3. Simple Machines
One way is to magnify an effort force so that a smaller effort can be applied over a longer distance thus moving a large load a small distance.
Examples:
a crowbar being used to dislodge a boulder,
a nutcracker being used to crack a nut, 
or a block tackle pulley system being used to lift a large weight. 
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4. Simple Machines
The mechanical advantage of a machine is the ratio of the load force to the effort force. 
The crowbar, nutcracker, and block and tackle pulley system have a mechanical advantage greater than one. 
Other machines have a mechanical advantage less than one allowing magnification of the distance and speed of a movement. 
An example of this might be a fishing rod or baseball bat. 

5. Simple Machines Inclined plane -- a sloping surface, such as a ramp.
An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads.
The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed.
Examples: staircase, ramp, and bottom of a bath tub
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6. Simple Machines Wedge -- two inclined planes joined back to back.
Wedges are used to split things.
Examples:
Axe
Zipper
Knife

7. Simple Machines
Screw -- an inclined plane wrapped around a shaft or cylinder.
This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated.
Examples:
Bolt
Spiral staircase
wood screw
Corkscrew
screws on light bulbs

8. Simple Machines
Wheel and axle -- a wheel and axle has a larger wheel (or wheels) connected by a smaller cylinder (axle) and is fastened to the wheel so that they turn together.
When the axle is turned, the wheel moves a greater distance than the axle, but less force is needed to move it.
The axle moves a shorter distance, but it takes greater force to move it.
Examples:
Door knob
Wagon
Toy car
Bicycle gears
Screw driver

9. Simple Machines
Pulley -- a wheel that usually has a groove around the outside edge.
This groove is for a rope or belt to move around the pulley.
Pulling down on the rope can lift an object attached to the rope.
Work is made easier since pulling down is assisted by gravity.
Examples:
Flag pole
Crane
Elevators
Window blinds
Source:

10. Simple Machines
Lever -- a straight rod or board that pivots on a point known as a fulcrum.
The fulcrum can be moved depending on the weight of the object to be lifted or the force you wish to exert.
Pushing down on one end of a lever results in the upward motion of the opposite end of the fulcrum.
Examples:
Door on hinges
Seesaw
Hammer
Bottle opener

11. Classes of Levers
The class of a lever is based on the relative position of the load, effort, and fulcrum.
Levers are classified into 1st class, 2nd class and 3rd class levers.

12. Classes of Levers
1st class:
Crowbar
Scissors

13. Classes of Levers
2nd class:
Nutcracker
Wheelbarrow
Doors

14. Classes of Levers
3rd class:
Tennis racket
Tweezers

15. Questions about Simple Machines
What is a simple machine?
What are the 6 simple machines?
How does each simple machine work?
How does each machine make work easier?
What are the classes of levers and how do they work?
What is mechanical advantage?