Sunday, August 14, 2011

Density

Density

So today I jumped out of bed really somewhat energetic and decided that I would do 2 comics today. So here’s the first one, you can expect another one before midnight.

Yeah, so density is basically how much weight something has. Most of the time it is easy to see what is denser than what. After all, most people can see that you are denser than roll of toilet paper. (Although some people may be described as denser than a roll of toilet paper, but that’s a different story)

By the way, water has a density of 1000 kg per m of volume. This is also known as a density of 1000. So you’ve got to have over a density of 1000 to sink under the water. Humans happen to have a density of about 1000, which is why a dead body can float on water. However, humans tend to breathe oxygen into their lungs when they are alive, so that increases their density, and they fall below the water. The least dense thing, is something called an interstellar medium which is basically some stuff that exists in space. This is followed by earth’s atmosphere. The leas dense MATERIAL however, is…(trumpets playing)…AEROGEL! (Isn’t that lovely). The densest thing is a black hole, which is basically an exploded star, and the densest material is platinum. Oh by the way, salt water happens to be slightly denser than fresh water (it has a density of 1030) so it’s easier to float on salt water than fresh water. There doesn't seem to be much difference though.

So most of the time, you just want to find out whether something is denser than water. To do that, you just put that thing on the water, push it down and see if it sinks. If it sinks, it’s denser than water, if it doesn't, it’s less dense than water. If you wanted to find the EXACT density of something, you would use this super simple formula:

 \rho = \frac{W_a}{W_a + W_w - W_b} \left (\rho_{water} \right ) \,

where:

ρ is the density of the composite material, in g/cm3

and

Wa is the weight of the specimen when hung in the air

Ww is the weight of the partly immersed wire holding the specimen
Wb is the weight of the specimen when immersed fully in distilled water, along with the partly immersed wire holding the specimen
ρwater is the density in g/cm3 of the distilled water at testing temperature

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