Simple Machines Notes: All you really need to know

Simple Machines
Give me a lever long enough, and a fulcrum on which to place it, and I will move the world Aristotle

Definitions:
• Work
• Energy
• Load
• Input force
• Trade-off
• Mechanical Advantage

What are simple machines?
• Simple machines are tools that make work easier
• They have few or no moving parts
• Simple machines make work easier for us by allowing us to push or pull over increased distances
• Use the idea of spreading force over distance: if you push further, you can use less force .
• There’s a trade-off of energy when using simple machines.

Simple machines are used to make work easier by
• Changing the direction of a force,
• Provide a mechanical advantage

Types of Simple Machines

Ramp or Inclined Plane
• A flat surface that is higher on one end
• You can use this machine to move an object to a lower or higher place.
• Trade-off : The way an inclined plane works is that to save effort, you must move things a greater distance
• The longer the distance of the ramp, the easier it is to do the work

Wedge
• A wedge is a simple machine used to push two objects apart
• A wedge is usually made up of two inclined planes
• Trade-off : To split something apart really wide, you have to push the wedge a long distance.

Screw
• An inclined plane that winds around itself
• a wedge at the tip
• A screw is like the ramp -the width of the thread is like the angle of an inclined plane The wider the thread of a screw, the harder it is to turn it.
• Trade-off : The distance between the threads depends on the slope of the inclined plane - the steeper the slope, the wider the thread

Lever
• A lever is a board or bar that rests on a turning point called the fulcrum
• An object that a lever moves is called the load
• The closer the object is to the fulcrum, the easier it is to move

Wheel & Axle
• A wheel with a rod, called an axle, through its center lifts or moves loads
• The axle lets the wheel turn
• The circle turned by the wheel is much larger than the circle turned by the axle.
• Trade-off-: The larger the diameter of the wheel, the less effort you need to turn it, but you have to move the wheel a greater distance to get the same work done.

Pulley
• In a pulley, a cord wraps around a wheel
• As the wheel rotates, the cord moves in either direction
• When a hook is attached to the rope you can use the wheel’s rotation to raise and lower objects.
• Pulleys let you move loads up, down, or sideways
• Trade-off - as you increase the number of pulleys, you also increase the distance you have to pull the rope
o In other words, if you use two pulleys, it takes half the effort to lift something, but you have to pull the rope twice as far

adapted from http://science-class.net/7thGTPAP_Notes/Notes_Work_and_Simple_MachinesGTPAP.htm