in this video I'll talk about a problem related with the Hookes law so here we have given a spring and which stretches by 20 centimeter 150 Newton object is loaded onto this one so let's say if this is 150 Newton then this elongation is a 20 centimeter and the line this line here means the position without no mass that means if I just take this mask off then the spring will come back to this position so all the measurements are done from this line here so when there is no mass and this with the mass this is what we call the elongation or the stretch in the spring or we simply call X or the displacement and we have and in order to calculate the spring constant by given force and the displacement we're going to use the Hookes law the Hookes law tells you the four is equal to minus K times X K is called the spring constant this is the spring constant which is a constant for a spring it does not change if you have the same spring what changes is the force and the displacement if we apply more force than the displacement will be more but K the spring constant will remain exactly the same in most cases okay so the what is the negative sign here let me explain it a little bit about the negative signs although it is not relevant for this topic but I'll explain anyway so there are two forces acting on - this is spring and - this mass the one force is the weight is weight which is mg and the spring tries to pull it back so there is this force here this is called the restoring force or the force by the spring that's the restoring force which is opposite to the the applied force or if the the displacement increases the more we pull it down the more will be the restoring force that means the the restoring force and the displacement are in opposite direction that's what does the negative sign means here okay if we do not need use the negative sign if you just use F then that means this is the applied force okay with the negative sign that means the restoring force anyway so now let's guess to get back to here the magnitude of this force would be simply K times X and we have to calculate K as it is asking here what is the spring constant so K will be simply force divided by the displacement the force is already given which is 150 Newton and the displacement is 20 centimeter and who had to change the 20 centimeter to meter so just divided by 100 and it'll be point 2 meter so we have calculated the spring constant which is 750 Newton our Newton per meter the unit for K will be Newton per meter this is Newton and this is meter so it will be Newton per meter the second part of what is asking here is what is the screech in the spring if 20 kilogram object is hung from it so now we are given a different mass now so what happens or how much will be the elongation in the spring so let's calculate this one the first thing we need to calculate what is the weight of the 20 kilogram object so this is the mass which is 20 kilogram the weight or the force is equal to M times G the mass is 20 kilogram G is 9.8 so the force we have is now 196 Newton again this is a Hookes law force is equal to K times X and I'm simply using the magnitude of the force and so K will be force divided by X will be force divided by K the force is now hundred ninety-six Newton and KL as a mentor k does not change for a spring it remains the same the only thing that changes is the force and the displacement K remains the same so I already had calculated K which is 750 now if I divide what I will get is point two six meter that corresponds to twenty six centimeter all right so this is how you use the Hookes law to calculate either the displacement or find out the spring constant of a spring so this is it from the Hookes law again if you have any questions any comments any suggestion write down in the comment section below and do not forget to Like share and subscribe the channel