Tuesday, 28 November 2017

Viscosity; Newtonian and Non-Newtonian Liquids

Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.

Consider how these liquids look when you pour them:
  • Water
  • Milk
  • Oil
  • Egg yolk
  • Honey

Newtonian Liquid: only temperature affects its viscosity

Non-newtonian liquid: other forces/factors affect its viscosity

Examples of Non-Newtonian Liquid: 

Corn starch and water
When a force is applied to the polymer chains, they straighten out and entangled with each other, raising the viscosity 

There is a product that is used in some safety equipment (knee pads, maybe helmets) that is like cornstarch and water and works to absorb the force and protect you called D3O. See https://www.acs.org/content/dam/acsorg/education/resources/highschool/chemmatters/issues/2016-2017/February%202017/chemmatters-feb2017-d3o.pdf for more details.

Neat Videos:

This next video demonstrating D3O is not something you can try yourself. Watch this only after asking permission from your parents when you are at home.

Sunday, 26 November 2017

Paper Airplanes

Why do airplanes fly? It's harder to explain that some people might think. Check out this website for an approachable, yet comprehensive overview of the myths and reality of what makes airplanes fly:


It is Newton's three laws of motion that are the key to the explanation (not Bernoulli's Principle, which partially correct but overly simplistic.)

Newton's Three Laws of Motion

Newton's Three Laws of Motion in Plain English 
Ultimately, what best explains what gives wings lift is that the wing must push a lot of air down.

What a better way to explore flight than by making paper airplanes. Here are some straight forward instructions:

Very Easy:


The Tail Spin