Think about most of the forces you see in Daily life
You're pushing a box your weight. Which is a force acting downwards,
hammering a big nail into the ground. All these forces, if you notice, are acting perpendicular to the surface
A force exerted by an object perpendicular to the surface is given a special name.
It's called Thrust. It's the total force acting perpendicular to the surface.
What will be the unit of thrust in the SI system? Can you guess?
You should have got this one.Thrust is nothing, but force so the SI unit of thrust will be the same as that of force.
Newton. The SI unit of thrust is Newton.
What's pressure?
Now I don't want the definition or the formula. I want you to understand it. Let me give you a couple of examples.
Take a pencil and keep it between your thumb and index finger,
with the tip touching the index finger and the other end touching the thumb.
Now apply equal force from both ends towards the pencil for a few seconds.
Release the pencil and observe the two fingers. To be precise, observe the depression you see in the fingers
You notice that the depression in your index finger, is much more as compared to the depression in your thumb.
Why does that happen? Before we answer that, let me give you a second situation.
When you stand on loose sand, you see that your feet go deep into the sand.
Now if you lie down on the sand, will you go just as deep into the sand?
No, you won't
But if the force exerted in both the cases is the weight of your body, then why is the depth in the first case more?
That's where the concept of pressure comes in.
Pressure is nothing, but the force per unit area. If we're talking about thrust, it would be thrust per unit area.
If the thrust is constant and the area is more, then the presssure will be lesser
and if the area is less then, the pressure will be more.
Pressure is inversely proportional to the area on which the thrust is applied.
Now we can understand the two situations in terms of this formula.
What happened in the first situation?
As we apply an equal force from both ends, the need for the Newton's third law,
The pencil will also apply an equal and opposite force on the fingers, as the depression was more on the index finger.
That's because the area on which the tip of the pencil applies a force on
is lesser, as compared to the area on which the other end of the pencil applies a force on.
As the area is lesser the pressure is more, and that's why the depression is more.
Can you understand the second situation using this concept?
In the second situation, the area on which your feet lie, is lesser as compared to the area on which your entire body lies,
and that's why, the pressure is more when your feet are on the sand as compared to when your entire body lies on the sand,
which explains why the depth here is more.
What is the SI unit of pressure?
As its force over area, it would be newton per meter square.
This is the SI unit of pressure, and this is also called as Pascal.
One pascal is one Newton over one meter squared
This has been named after a famous scientist called Blaise Pascal, who had conducted extensive studies in this area of science
Let's quickly recap, what we learned.
Whats thrust? It's the total force acting perpendicular to the surface, and
What's pressure? It's the thrust per unit area.
If the same amount of thrust is applied on a lesser area, then the pressure will be more.
Captions Contributed by Godwin.
