You what Archimedes?

You are supposed to have run through the streets of Syracuse naked when you discovered upthrust? Nice.

Saying that, I do like upthrust. It stops you from drowning and instead makes you float. The principal goes;

'When a body is totally or partially immersed in a fluid, it experiences an up thrust equal to the mass of fluid displaced'.

Supposedly Archimedes discovered this law while taking a bath. He noticed that the level of the water in the tub rose as he got in, and realized that this effect could be used to determine the volume of the object.

Water is assumed to be incompressible, so the submerged object would displace an amount of water equal to its own volume.

He then found that by dividing the mass of the object by the volume of water displaced, the density of object could be found.

He is said to have used this idea to prove that a crown was made of lesser materials, rather than gold, as he showed the crown to be less dense.

Yay for Slow Moving Spheres!

­­­­Let me tell you a story, boys and girls, about one Sir George Stokes.

He came up with a mathematical description of the reactionary force that works against a sphere moving through an inactive, viscous fluid at a low velocity. (Very exciting, I know.)

His law; Stokes' Law is written as: Fd = 6πμrv

• Fd is the drag force of the fluid on a sphere.
• μ is the fluids viscosity.
• v is the velocity of the sphere.
• r is the radius of the sphere

While Stokes’ Law is straight forward, it is subject to some limitations. Specifically, this relationship is valid only for laminar flow. Laminar flow is defined as a condition where fluid particles move along in smooth paths in fluid layers gliding over one another. This means his expression only works for as the title states; for slow moving spheres, as a fast object would not travel with laminar flow and a sphere is only relevant as the expression requires a radius.

What I'm trying to say is it's not very relevant in most situations. Luckily, good old Stokes is better known for other works. (Why I did not cover them, I do not know!)

Without force, I can still move...

Just not start or stop, in other words accelerate. I'd be going on and on forever at a constant velocity. Luckily there's forces such as friction to stop me doing this - otherwise we'd be able to create perpetual motion. However, it is interesting (or at least I think so,) that I can still move at a constant velocity without a resultant force. It is only when forces are unbalanced, (skewed in one direction) that I will accelerate, either with a positive or negative magnitude. This is the essence of Newton's first law.

His second law covers this too, with the simple equation F= ma (Resultant force = mass x acceleration)

If my F= 0, it is clear to see that I will not accelerate.

What I think is more important about this second law is that it links acceleration to mass, and thus gives mass (a very hard concept to explain) a definition (though there are several); the measure of an objects resistance to acceleration.