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

Before you read this, I suggest you read posts 17.49 and 17.50. In post 20.14, I mentioned the belief that acidic drinks could make our body fluids more acid; similarly, many people believe that eating alkaline foods will make their body fluids less acidic. To find out more about acids and alkalis, and the pH… Continue reading 20.16 Homeostasis 1 – controlling the body’s chemical composition

I suggest that before you read this, you read post 20.14. In post 16.18, we saw that a cell is conventionally considered to be the smallest part of us that is alive. Bone contains four types of cell: osteoblasts, osteoclasts, osteocytes and endosteal cells. In this post we will consider only the first two. Osteoblasts… Continue reading 20.15 Osteoporosis 2 – bone cells