Hooke's Law (How is Hooke's law applied to spring)

 Hooke's Law

How is Hooke's law applied to springs?

Every single spring has the ability to stretch. And this ability to stretch is called Elasticity. Now, the amount that an object stretches depends on the force acting on the object.
Therefore, the relationship between the force and the amount the spring stretches by is given by Hooke's Law. This is shown below:


                                                            F = Kx     or       F = -Kx

F -   Force acting on the object
K-   Proportionality Constant
X-   Change in the length (Extension)

• Normally in some cases, the above formula would have a minus in front of the K. This just tells us that hooke's law if doing the opposite. What this means is as a certain mass pulls the spring down, the hooke's law is a law trying to bring the spring back to its original natural length. But in normal situations, the minus sign is not used.

• Now, lets suppose we have a spring, and it is stationery, then its extension is zero. But, lets suppose we take a very heavy mass which in turn acts on the spring. Then, the distance in which the spring stretches is called the extension (X). The reason as to why the spring stretches as extra distant, is because when a pulling force acts on the spring, mainly downwards, a tension is applied with also gravity acting, causing it to move or stretch downwards.

Therefore, Hooke's law states that the force acting on a object ( in this case the spring) is directly proportional to the extension or stretch in the object.

This is shown below on a graph:

Density (How does a connon ball float in mercury)

                                               Density

How does a cannon ball float in mercury?

Mercury is an interesting substance that  has some unusual properties. Now, in terms of its density, this is where mercury becomes interesting.

To start-of,  density is the mass per unit of volume. This is the mass of the substance compared to its volume.
This can be shown as

                                                         Density =  Mass/Volume

Now, looking at Mercury it is a substance with a high density. If we place a cannon ball into mercury, it will float. This is because the cannon ball has a lower density than mercury. But what do we mean by the density. If you look at mercury, it is made up of substances that occupies a huge volume. Whereas the cannon ball may have a huge mass and its volume is compact within that mass. Therefore, as the cannon ball lands unto the mercury, the mass and the volume of the ball is shared amongst the huge volume of the mercury.  This is why the cannon ball floats on the mercury, as well as why the mercury is more denser than the cannon ball.