Before you read this, I suggest you read post 20.25 Normally, we think that objects spontaneously minimise their potential energy so that, for example, an object falls to the ground when it is released (post 16.21) and a stretched spring recoils when released (post 16.49). But this can’t be true for the molecules in a… Continue reading 20.26 Boltzmann and other distribution laws
Before you read this, I suggest you read post 17.5 Liquids and gases are both examples of fluids – things that flow into the space available to them (post 16.37). In post 17.5, we saw how the pressure in a liquid increased with depth. Normally, we think of the pressure in a gas as being… Continue reading 20.25 Pressure distribution in fluids
Before you read this, I suggest you read post 20.23. In post 20.23 we saw that, when a gas is compressed, it is subjected to the same pressure in all directions, so that its resistance to compression is given by its bulk modulus, B, defined by B = –Vdp/dV (1) (post 20.20) where V is… Continue reading 20.24 Adiabatic compression of a gas
In post 20.20 we looked at isotropic compression of a solid object. In a gas, or a liquid, the pressure acts equally in all directions (post 17.5), so when a gas is compressed it is subjected to isotropic compression. Then resistance to compression is then given by the bulk modulus of the gas (post 20.20).… Continue reading 20.23 Isothermal compression of a gas
In post 20.20, we saw that there was a relationship between the Young’s modulus, E (post 20.2) and the bulk modulus, B (post 20.19) of a material. The relationship is given by E = 3B(1 – 2ν) (1) where ν is the Poisson’s ratio (post… Continue reading 20.22 Relationship between Young’s modulus and shear modulus
In post 20.20, we anticipated that there must be some relationship between the Young’s modulus, E (post 20.2) and the bulk modulus, B (post 20.20) of a material. The relationship is given by E = 3B(1 – 2ν) (1) where ν is the Poisson’s ratio (post 20.5) of the material. We shouldn’t be surprised by… Continue reading 20.21 Relationship between Young’s modulus and bulk modulus
Before you read this, I suggest you read post 20.2. Let’s think about a solid sphere surrounded by a fluid (post 16.37). If the pressure in the fluid increases, the force on the ball increases because pressure is simply a component of a force divided by an area (post 17.5). We will assume that the… Continue reading 20.20 Deformation of objects – isotropic compression
In post 20.2 we saw that forces can change the dimensions of an object; they can also change its shape. Change in shape without changes in dimensions is called shear. The picture above shows a cube ABCDEFGH. Let’s think about what happens when we apply a force f (posts 17.2) perpendicular to the line BF… Continue reading 20.19 Deformation of objects – changes in shape
Before we start to think about this question, we have to recognise that very few scientists are ever really famous. I believe that Charles Darwin, Albert Einstein, Marie Curie, Alan Turing and Stephen Hawking are all names that are recognised by very many people (although there is no picture of Hawking on Pixabay, http://www.pixabay.com ).… Continue reading 20.18 How do scientists become famous?
In post 20.16 we saw how the body was able to control its chemical composition; in this post I am going to write about how it controls its temperature. This post is mostly about temperature control in humans. We need to maintain our bodies at about 37oC to provide the optimum conditions for the chemical… Continue reading 20.17 Homeostasis 2 – controlling the body’s temperature
