 Welcome back to another session in this session. We are going to discuss how do we measure force so in the previous session We saw that forces Force is an agent of change. Isn't it? So we discussed this force is equal to an agent of Change and what are we saying is changing? So we are saying the inertia the state of inertia is changing So a state of inertia of rest motion direction or shape anything can change and force is the cause so hence If you see this force is a cause and cause is leading to some effect What is this effect? This effect you will learn little later is Acceleration Okay, so acceleration is what results once force starts acting on an An object later on will see that this force has some qualification that is it has to be unbalanced and all that But for the time being please understand that if some unbalanced force what is unbalanced force will discuss a little later Just have some patience so if there is an unbalanced force acting on an object it will lead to its acceleration and This is what manifests, right? So this is what we can see so we can see that this is the manifest manifestation That is display of effect of force manifestation of Effect of force manifestation means it you know This is how we get to know that force is being applied So manifestation of effect of force. So if you can measure acceleration, then you can measure force as well So this is how we measure force and how do we define? force and what is the unit of force so unit of force is given or Has been you know the unit of force is Newton right so hence we say unit of force Unit of force now unit of force whenever we say unit of force We do mean SI unit that the standard international standard unit, right? So unit of force is Newton and it is written as N E W T U N obviously named after Sir Isaac Newton and In short form it is written as capital N Okay, so hence unit of force is Newton. So you know that Whenever we have any scientists name after any unit we start the unit with small letter So you can see that the letter n is small But while we are writing the shorthand abbreviated form, we will write capital N So this is unit of force. Now, how do we define one Newton? So for that, let us say we have an object of one kg. Okay, so here is one object of one kg Let me redraw it so that Okay, so hence. Yeah, so what I'm going to do is I'm going to redraw this. So let us say we have an object of one kg One kg. This is one kg mass. So all of you know kg is the unit of mass So let us say we have one kg mass and we are applying some force on to this One kg mass and let it be f. Okay. Now if there if the effect is if the acceleration acceleration produced so if you if you see if you Measure the acceleration produced in this case if it happens to be one meter per second square So what is acceleration we had studied in previous chapter? So if the acceleration produced on this one kg mass is one meter per second square, then we say That this f is nothing but one Newton force Once again, so if you have an object, which is one kg, you can see this is one kg object And you are applying a force which is something which we don't know right now Let's say and the effect. So this is the effect guys. So the effect of application of that one On that force is the acceleration of one one meter per second square on what mass one kg mass Then we say that force is one Newton. So how do we define? So we can define one Newton like this. So let's define one Newton. So one Newton is the force Which When Which when applied which when applied applied on A one kg mass One kg mass object produces produces produces an acceleration An acceleration of one meter per Second square, right? This is what is the definition of One Newton force. So now we have defined the unit of force now this Thing which we have defined is definition The basis of the definition is Newton's second law of motion Newtons Second law, but we are going to discuss this Little later, right? But Since we have to define a unit of force. So I have given you this definition now Once we deal with Newton's second law of motion, you will understand how and why this definition came into being