Air - The Thing Which Keeps us Alive Could Mean our Demise

Air is all around us all the time. It surrounds us every single minute of our lives, from start to finish: literally. Air is extremely important, and without it life may never even have come into existence. Air is mixture which helps us do things such as breathe, make fires and fly aeroplanes. One tiny change in the composition of air and we might have had very different lives, if none at all!  

A common misconception is that air is just one ‘element’. This is completely untrue! Air is not on the periodic table (you can check if you like). Air isn’t even one simple compound. In fact, air is actually a mixture of a variety of different elements and compounds in gaseous form, the most notorious of which being oxygen. However, this is not the gas in most abundance, in fact if it was we would most probably be dead, as pure oxygen is poisonous!

Air is actually made up mainly of nitrogen (around 78%), oxygen generally only makes up about 20-21% of air. There are also small amounts (around 1%) of noble gases such as argon and helium in the air. Finally, air contains substances essential for plant life: carbon dioxide (0.03%) and water vapour (0.97%, but it can vary!) Plants need carbon dioxide and water for the process of photosynthesis, where they convert these substances to glucose and oxygen in the process of photosynthesis. You may have heard of humidity levels. Since the amount of water in the air can vary, this can raise or drop humidity levels. It can go from 4% to 0.5%!

Air however does not only contain these set substances. It also contains minutely small amounts of other substances such as aerosols (which are tiny particles of dust from the ground or from volcanic ash.) If you can imagine zooming up into the sky, the composition of air there would be very different. There lies the notorious gas known as ozone, which environmentalists are currently making a big fuss about (due to the theory of global warming). There is also a lot more helium and hydrogen up there, as they are lighter elements, less dense than the others, so when they float up the others sink down.

You have probably heard of air pressure as well. This is just basically the weight of the air pushing down on everything on the earth – including us! Air pressure is measure in something called Pascal units which is just how many kilograms of ‘weight’/’force’ (measured in Newtons – “N”) act over 1 m² of area. So if 3kg of air was pressing down on 1 m² of area then the air pressure would be 3 Pascals. However the real pressure of the air comes nothing close to that. In fact for every 1 m² of area on the earth, air pressure results in a force equivalent to the weight of a large elephant pushing down on it! You may ask why we aren’t crushed by this force. This is because the blood in our bodies pushes out with an equivalent pressure and the two cancel out. This also explains why when we enter different areas of pressure, for example when flying on a plane, sometimes people get nosebleeds as the difference in pressure causes the blood vessels to expand and burst. Imagine if you entered a vacuum (space) without a special suit, you would just burst due to the pressure of your blood being too strong for your body to withstand!

physics.org | Explore | Radiation dose chart

Just came across this while looking at radiation from mobile phones on the 'physics.org' website. It shows how much radiation you can get from doing different things and loads of other random information. Thought it might be interesting - enjoy. (Click here for a bigger view.)

Elasticity - How does it physically work?

I was reading about elasticity and came across the basic principles:

• 
  
• Every material has a certain degree of elasticity
• There is a point, called the elastic limit, where the material permanently deforms and can't be returned back to it's original shape (it gains a new elastic limit as well). This is also called plastic deformation or plasticity.
• Robert Hooke described the amount stretched as directly proportional to the force it would produce and vice versa (e.g. a bigger gravitational force acting down upon the elastic material - hanging a weight off of it - would produce a bigger stretch/extension)

However, I couldn't quite understand how this actually worked on a molecular level. It took me a while to find all the information, but I eventually understood (after much searching on Google!).

So here is the explanation I collected up (from various sources):

Basically, materials can stretch due to inter-molecular forces between atoms. There are different charges in different parts of the material and these attract. If you try to squash the material like charges repel too much and so the material tends to try to stretch out again. If you stretch the material the opposite charges attract too much and the material tends to attempt to go back to its original shape. This shape is the shape in which the material is balanced: there is an equal amount of attraction and repulsion and so this is the preferred state for the material.

However, there is also the aspect of the elastic limit. This works because beyond a certain point the atoms become to far apart or close together to be pulled back into their original positions. The atoms have so much force exerted on them that they displace. However, once they have displaced they will settle in their new positions and assume a new elastic limit. This explains why elastic bands snap: the atoms move so far apart from each other that the whole material gets pulled apart!

I hope this makes things slightly clearer. If you don't understand anything just comment below!

Difference Between Centre of Mass and Centre of Gravity

Whether it makes a difference or not all depends
on size...

Now, as I mentioned in my previous post, the terms 'centre of mass' and 'centre of gravity' can be used almost interchangeably. However, this is only when we refer to relatively small objects, such as those which we find on the earth.
The difference between centre of mass and centre of gravity is fairly simple.
The centre of mass is a single point inside (or outside) any object where all of its mass effectively acts. In a regular 3D shape, such as a sphere, this would be the dead centre, however in a more complex shape it would be different.
The centre of gravity however, is where all gravity acts on an object. On earth the centre of mass is practically where all gravity acts so they can be used interchangeably. However, we know that gravitational pull depends on two things: distance between two objects and the mass of the object. The mass of the object will obviously always stay the same, however the distance from the object can change.
Consider an object as big as the moon. The distance from the earth on one side, would be much smaller than the opposite side. This means that since there is a substantial difference in pull between different parts of the 'object', the centre of gravity will be affected.
So there you go. There is always a difference between centre of mass and centre of gravity, but sometimes it is so minute that we consider it insignificant. This is due to the object being fairly small. However as the object gets larger, we begin to feel the need to distinguish between the two.
If you have any questions then, again, please feel free to leave them in the comments box below.

Unbelievable Experiment Demonstrating Centre of Gravity

What happens in the experiment:

Two forks seemingly magically balance on the rim of the cup, with the support of a mere toothpick.


Watch the video
Here is a video of an experiment I did (see it on youtube).

How it works:

This is due to the law of centre of gravity.
This law states that every objects has a point, where all gravity will effectively act. This is the midpoint of all the mass in the object. In a simple shaped structure such as a cube, this will just be in the middle, as there is an equal amount of mass in all directions of that point.
However, in the complicated, but symmetrical structure of two forks wedged together, the centre of gravity will act somewhere in the air (that is why two forks dip inwards if you hold them by the prongs)! I know this is complicated to understand, but the rest of the object does not affect the gravitational pull. If you piled up ten more forks, equally on both sides, the structure would still balance (if you had a really strong toothpick!).
Some people may use the term 'centre of mass' as well. On earth we can use these terms interchangeably, however in different gravitational fields, there is a difference.
If you are confused about the difference between centre of mass and centre of gravity, don't worry, as I will go over this in a later post, if you can't wait till then, click here.

View us on YouTube!

I have made a YouTube profile on which I will be posting a variety of different videos and experiments relating to this blog. Feel free to check it out now at http://www.youtube.com/user/Rockhoppable?feature=watch. I'll post new videos on the blog as well so you don't miss out!

In my next post, I'll tell you about center of mass, and how to do an amazing experiment using this simple law!

How to improve your life with a 'P'...

I've thought up a little system composed of ten words. These words describe and include ten things that apply to everyone in the world, and will make your life better if you improve on them. I know it is quite random, but oh well.

1) Politeness - be nice to other people!
2) Punctuality - be on time, don't be late and get yourself organised!
3) Procrastination - stop putting off tasks you should be doing. It will make life much easier.
4) Personal Hygiene - this is obviously essential...
5) Prayer - may only apply to those who are religious and actually pray, but communication with a divine being is proven to make you feel a lot more satisfied!
6) Priority - if you get these straight, then workloads and commitments seem to sort themselves out...
7) People skills - your social life is obviously important, and being able to communicate with others effectively is a must.
8) Perseverance - when you get things done there is that great sense of accomplishment.
9) Perspiration - this can refer to both exercise (keep a healthy lifestyle), and working hard in whatever you do, to do it the best you can.
10) Personality - probably the most important! Be yourself and be a good person!

Improve on these ten 'P's and I can guarantee everything will seem a lot better!