Topic 1.1 – Simple Machines Levers

Way back when… The earliest machines were very simple devices. Levers to pry rocks out of the ground Ramps to help raise rocks as walls were built The first machines all had something in common… THEY ALL DEPENDED ON PEOPLE OR ANIMALS FOR THEIR SOURCE OF ENERGY

Roman Aqueducts Thousands of years ago, Roman engineers developed a mechanical system for transporting water for many kilometers. They were made of: Pumps Ramps Distribution systems

Meeting the same need in different ways Water is a NEED Before we had taps with pumps like we do now, engineers used gravity to help move water through pipes. A sakia was used Had a series of buckets attached to long ropes which was draped over a wheel Animals such as donkeys turned the wheel, raising the buckets of water

Archimedes does better Archimedes invented a screw to help move water. More efficient ways were always looked for An Archimedes screw can move large amounts of water

Simple Machines A simple machine is a tool or device made up of one simple machine Lever Inclined Plane Wedge Screw Pulley Wheel and Axle

Lever A lever is a rigid bar or plank that can rotate around a fixed point called a fulcrum.

Levers are used to reduce the force needed to carry out tasks like: Pulling nails Opening bottles Hitting a baseball Cutting Paper With a lever you can move a larger load than you could without using it.

Diagram Effort Force Load Force

3 kinds of levers 1. First class lever 2. Second class lever 3. Third class lever

First Class Lever A first class lever has the fulcrum between the load and the effort pliers Scissors See-saw Examples:

Second Class Levers A second class lever has the load between the effort and the fulcrum                           Examples: Stapler Wheelbarrow Nut Cracker

Third Class Lever A third class lever has the effort between the load and the fulcrum. Examples: Fishing rod Tweezers

We build machines for two reasons: 1. To go faster or further Distance/Speed Ratio 2. To make ourselves seem stronger or increase the amount of force we can apply Mechanical advantage

Mechanical Advantage A person on their own would never be able to lift a car. A lever could make this possible!!!! A scientific explanation for this is the lever provided mechanical advantage.

The mechanical advantage of a machine is the amount by which a machine can multiply a force The force applied to the machine is called the input force The force the machine applies to the object is called the output force FORCES ARE MEASURED IN NEWTONS!

Mechanical Advantage (MA) = Output Force Input Force If the Mechanical Advantage is: Less than 1  The amount of force you are putting in is MORE than the force you are getting out. Is equal to 1  The amount of force you are putting in is THE SAME AS the force you are getting out. More than 1  The amount of force you are putting in is LESS than the force you are getting out.

Example: If we had a first class lever that takes 45 N to lift a 45 N weight. MA = 45N = 1 45N This means, the amount of force you are putting in is the EXACT same as the force you are getting out.

If we had a first class lever that takes 45 N to lift a 180 N weight MA = 180N = 4 45N This means, the amount of force you are putting in is less than the force you are getting out.

If we had a first class lever that takes 180 N to lift a 45 N weight MA = 45N = 0.25 180N This means, the amount of force you are putting in is MORE than the force you are getting out. This is a bad mechanical advantage.