Theory behind the slime

If you could check out cornflour up close, you would see that the powder is made up of particles that are relatively big with edges that are jagged and uneven. When you slowly move the slime with not much force, the slime acts like a liquid as the particles have space to move around each other. However if you add more force, the jagged bits get snagged on one another and the slime acts like a rock. Once you stop stirring it quickly, the particles can slide past each other again, so the slime acts like a liquid.

This ‘stir-thickening’ of the cornflour slime shows that the material is a Non-Newtonian fluid. This means that the material does not follow the properties described of fluids by Newton’s law of viscosity. This law defines the relationship between the sheer stress to sheer rate of a liquid at a given temperature and pressure (in the case of a Non-Newtonian fluid, the viscosity is not constant and is dependent on the sheer rate i.e. in this case, the amount of pressure applied).

How can this science be used?

Non-Newtonian fluids can be handy! Plenty of research is being done about how to use this special material in modern technology. Local and international scientists as well as engineers have been developing liquid body armour using non-Newtonian fluids, since they are really good at stopping bullets!

In 2010 a number of articles were released about the development of a speed bump dynamically changed depending on how fast cars were travelling over it! If you travel over the speed bump at a slow speed the fluid inside the speed bump would move out of the way and you’d barely feel the speed bump. However, if you travel over the speed bump too fast the speed bump would react quickly to the increased force and become almost solid… making your car bounce and reminding you to slow down!

(C) Fizzics Education (Used with permission)