reactions of acid water and oxygen with iron

REACTIONS:

WATER:
Air-free water has little effect upon iron metal. However, iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting and is familiar to any car owner.

OXYGEN:

Iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting and is familiar to any car owner. Finely divided iron powder is pyrophoric, making it a fire risk.

On heating with oxygen, O₂, the result is formation of the iron oxides Fe₂O₃ and Fe₃O₄.

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

3Fe(s) + 2O₂(g) → Fe₃O₄(s)

ACIDS:

Iron metal dissolves readily in dilute sulphuric acid in the absence of oxygen to form solutions containing the aquated Fe(II) ion together with hydrogen gas, H₂. In practice, the Fe(II) is present as the complex ion [Fe(OH₂)₆]²⁺.

Fe(s) + H₂SO₄(aq) → Fe²⁺(aq) + SO₄^2-(aq) + H₂(g)

If oxygen is present, some of the Fe(II) oxidizes to Fe(III).
The strongly oxidizing concentrated nitric acid, HNO₃, reacts on th surface of iron and passivates the surface.

https://www.webelements.com/iron/chemistry.html

force in levers

Forces with levers :

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A lever is a mechanism that can be used to exert a large force over a small distance at one end of the lever by exerting a small force over a greater distance at the other end.

In general the effort force can be expressed as

F_e = F_l d_l / d_e         (1)
where
F_e = effort force (N, lb)
F_l = load force (N, lb) (note that weight is a force)
d_l = distance from load force to fulcrum (m, ft)
d_e = distance from effort force to fulcrum (m, ft)

http://www.explainthatstuff.com/toolsmachines.html
http://www.engineeringtoolbox.com/levers-d_1304.html
http://www.google.com.co/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjSxeyoy7rOAhXBdSYKHa11CHAQjRwIBw&url=http%3A%2F%2Fwww.slideshare.net%2Fphysicsgalle%2Fbalanced-forces-ppt&psig=AFQjCNHpdXkvSia6OaoGupzrX7gtu0JCbw&ust=1471046909708685

lever

History:

Levers have been used since prehistoric times for cultivation, excavation, and moving large objects. Such implements as hoes, slings, and oars were conceived and constructed to enhance human effort.
As early as 5000 B.C.E., a simple balance scale employing a lever was used to weigh gold and other items. A Greek device called a steelyard improved on these simple scales by adding a sliding weight to enhance precision. Around 1500 B.C.E., the shaduf, a forerunner of the crane, made its appearance in Egypt and India as a device for lifting containers of water.
The earliest extant writings regarding levers date from the third century B.C.E. and were provided by Archimedes—behind his famous remark Give me the place to stand, and I shall move the earth stands a correct mathematical principle of levers (quoted by Pappus of Alexandria) and of the various methods possibly used by builders.


http://www.newworldencyclopedia.org/entry/Lever 

Chemical and physical properties:

• Exceptionally strong relative to its weight
  
• A good heat and electrical insulator;
  
• of increasing importance
  
• It is a renewable and biodegradable resource.
  

  Chemical and physical changes:

  Good general rule: A chemical change changes the substance so that you can't ever use it the way you did before. A physical change retains the character of the substance.
  
  Burn a candle, and you can never burn that candle again. It has undergone a chemical change. Cutting that same candle into a bunch of small pieces is a physical change, because if you were to melt the wax and mold it into a candle like it was in the first place, you could still burn that candle. The little pieces of wax act just like the big piece of wax.
  
  I know, I know, it's not quite perfect, but it's still a good way to remember the difference.
  
  Same thing goes for wood. Burning wood is a chemical change, because you can't turn it back into a log that you can burn.
  
  Cutting wood into smaller pieces of wood is a physical change. Each individual piece of acts just like the bigger piece. You can pile a bunch of little tiny toothpicks together and they will burn just the same way a log does.
  
  Baking a cake is a chemical change. You can never get the uncooked flour and eggs and stuff out of that cake again.
  
  Heating ice to become water is a physical change. All you have to do is put it in the freezer and it's ice again.  
  

   

Lever

Lever

What is it?

A lever is a simple machine that is made up of a board or bar that rests on an object. The object that holds up the bar is called a fulcrum

Why do we use it?

Levers are used to make moving heavy objects much easier by using less force.

There are 3 parts to a lever.

1. Effort- the force that moves the lever

2. Load- the object the lever is trying to move.

3. Fulcrum- the point on which the lever moves.

First-class Lever

In a first class lever, the fulcrum is located between the effort and the load. 

Second-Class Lever 
In a second class lever, the load is between the fulcrum and the effort. 

Third-class Lever\
In a third-class lever, the effort is between the fulcrum and the load.

lever

fluidsanddynamics.weebly.com

http://ed101.bu.edu/StudentDoc/Archives/ED101sp06/cjhpyo/lever.htm

Simple Machines

A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. 

Usually the term refers to the six classical simple machines which were defined by renaisance  scientists:

Simple machines make work easier for us by allowing us to push or pull over increased distances.