Published via Ecency

One day, I ,AKA Phamzy, was curious about why petrol looks lighter than water, water looks lighter than generator oil, and generator oil is lighter than grease oil.

I know it has to do with friction, but I did not know what it was called. However, in senior secondary school, we were taught viscosity.

And what exactly is viscosity?

Viscosity is the frictional force between layers of a liquid. Petrol has a less viscous force when compared to water. In fact, I noticed that whenever I want to buy engine oil, these viscous forces have different values. For a generator, there is a specific one, and for higher engines like cars and trailers, we need a more viscous oil. In fact, the oil used in ships is very, very thick.

Now, let's talk about Newton's formula!

I checked a textbook some time ago and found out that viscosity is actually tangential force multiplied by the distance between layers, divided by the product of the velocity difference between layers and the area of the layer.

Alternatively, one can say it is force divided by the product of the velocity gradient and the area.

Remember, the velocity gradient is given by the difference in velocities of each layer divided by the height (distance) difference between the layers.

Check the image below for a better understanding!

What about the effect of a spherical object on a viscous liquid? Is it going to slow it down? Is it going to speed up?

What about the effect of mass on it? Actually, there is something we call terminal velocity.

Terminal velocity is the velocity of an object when the frictional force is equal to the weight of the object. So, mass cancels out after reaching the termnal velcity but an increment in mass will cause a corresponding increase in terminal velocity.

It is a constant velocity. No wonder skydivers only experience acceleration during the first few seconds of their fall.

Using stokes equation, one can determine the frictional force or let me say viscous drag.

So the Stokes equation is given by F = 6πηrv (where η is viscosity, r is radius, and v is velocity).

Check the image below for a graphical representation of terminal velocity for a ball falling into a viscous fluid.