Simple Machines

!!!!Simple Machines!!!! 

What makes humans different from other species?? 

Humans have the ability to share and pull ideas from others in a process called collective learning. Humans are the ONLY organisms that have the ability to use this advanced type of intelligence. During the study of human evolution at the beginning of the year, my classmates and I studied how our hominids started from making simple tools that would later evolve into complex machinery.

There are six devices that are known as the six simple machines.... 

What is a "simple machine": They are machines that change the direction and magnitude of an input force. They basically trade force for distance. 

Here are some basic concepts you must be familiar with to be able to understand how/why these machines work. 

Conservation of Energy - No machine can output more energy than was put into it. 

A useful way to characterize simple machines are to compare how large the output force is relative to the input force. Use the Mechanical Advantage Equation for this.... 

MA = Output Force/ Input force 

A simple machine would be considered ideal if it had no friction. When putting in effort, some of it is put is wasted trying to overcoming friction. Ideal Mechanical Advantage can be determined by the following equation. 

IMA: Distance In / Distance Out 

To figure out the final efficiency of your machine, use this equation.

Eff = Work Out / Work In 

Overall Simple Machines Work Like This ....... 

Simple machines multiply force. 

     They are trading a small force through a large distance for a large force acting through a                      small distance.  

                  

(It seems a little hard to grasp, but upcoming examples will help you to understand!) 

                                         

              Here are the 6 simple machines!!!  

         Pulley 

A pulley is a wheel that has a groove along its edge, where the rope is placed. This machine uses the principle of applying force over a long distance. The tension in the rope reduces the magnitude of necessary force. Complex systems of pulleys can be used to greatly reduce the force that must be applied initially to move an object.

                                                          

Cons To Using The Pulley:

Take this example, 

if you life 100kg by pulling with a force of 25kg, you are only doing a quarter of the work and using a quarter as much energy. 

However, the law of physics, ( Law of conservation of energy) states that 

you must always put in as much energy as you get out. 

If you want to raise a weight of 100kg a distance of 1 meter off the ground, you have to do the same amount of work (meaning you have to move the same force over the same distance). 

Even if you attempt to use a pulley to reduce the force you're using by a quarter, you now have to pull the end of the top four times further. 

Here are the equations to help you understand... 

Work = Force x Distance   (W=FD) 

   
     Less force = More distance 

     Less Force = Longer Time 

Pulleys sometimes have more then one wheel. Here is a diagram to help you understand how they work. 

Fun Fact::: The largest ancient Egyptian pyramid (the Pyramid of Khufu) was built with the help 

of a pulley.   

              Levers 

Levers are machines specifically used to increase force. They impressively accomplish many tasks only using two parts, and handle and the fulcrum.  The handle bar of the lever is called the "arm," this is the part you exert force on. The fulcrum is the point on which the lever balances. 

Here are some simple examples of levers we see everyday..... 

(In these examples, you will be introduced to 3 different classes of levers) 

This is what a 1st class lever looks like..... 

And here is a real life example.... 

(In this image, the woman uses the trolley to move a weight. The fulcrum is the wheel) 

This is what a 2nd class lever looks like.... 

Here is a real life example..... 

Finally, this is what a 3rd class lever looks like..... 

Here is a real life example...... 

       Inclined Plane 

The inclined plane is slanted surface that connects two levels together. They are used to lifts loads to different heights. The inclined plane (ramp) alters the way in which work is done. If the effort decreases, the distance must increase, and vice versa. 

Here are some examples of inclined planes.... 

     
   

Here is an example of how you can find the Mechanical Advantage of the Inclined Plane!

      Wedge 

A Wedge is a machine that tapers to a thin edge or point often used for piercing objects. The advantage of wedge is that it can reduce the force needed to do work. 

One may simply define a wedge as inclined planes back to back. However there are key differences...

     a wedge can have a curved surface 

     a wedge moves while an inclined plane remain in one place 

Theoretically, the wedge has a mechanical advantage equal to its length divided by its base, however, this theory is debunked when friction comes into play. 

Examples of a wedge..... 

 

     Wheel and Axle 

The wheel and axle are considered a simple machines because, they can produce leverage. Wheels on carts, (and this may surprise you) work like levers. The rim of a wheel turns a greater distance than the axle does. So, when you are pushing the wheels, there is more force at the axle than at the rim.  If, for example, a cart has, big wheels, they'll give you more leverage and overcome the force of friction at the axles.

Wheels also reduce friction by digging into the surface as they rotate, and thus turn around sturdy rods called axles. 

Examples:::: 

       

   Screw

A screw is a shaft that has an inclined groove along its surface. To get a linear force out of this machine, you must rotate the screw (apply a torque). This is often used to fasten objects together. 

Visual Aid.... 

Due to these initial simple machines, overtime, we have created more complex machinery to continue bettering our everyday lives. 


resources

http://teacher.scholastic.com/dirt/lever/whatlevr.htm

http://www.explainthatstuff.com/howwheelswork.html  

http://www.explainthatstuff.com/pulleys.html 

http://physics.about.com/od/physicsintherealworld/p/simplemachines.htm

http://www.cheops-pyramide.ch/khufu-pyramid/rope-roll.html

http://www.technologystudent.com/forcmom/lever1.htm 

http://www.mikids.com/Smachines.htm 

http://www.ohio.edu/people/williar4/html/haped/nasa/simpmach/Inplane.htm

Thank You For Reading!!! - Helena