Hello students we have already studied the Pascal’s principle and we move on to the third application of Pascal’s principle that is the hydraulic break we’re all aware that hydraulic brakes are used in cars and they use nothing else but Pascal’s principle the construction and working of hydraulic brakes is the most interesting application of the Pascal’s principle let’s take a look at the construction of the hydraulic brake now if you take a look at the diagram we know that the first thing we do in hydraulic brake is that we place a foot on the pedal now the foot placed on the pedal and the pedal is the first component of a hydraulic break so foot pedal is the first thing we need to know the second thing we need to know is that the foot pedal is connected to the master cylinder P and if you take a look at this black piston it’s the piston a so we say that the foot pedal is connected through the piston a to a master cylinder p  so every card for every vehicle has a master cylinder P now to this master cylinder p is connected a pipeline R if you take a look at the pipeline it contains a liquid and in case of a hydraulic brake it is obvious that this liquid will be oil which is commonly referred to as break oil this masters Cylinder connected to a wheel cylinder and for each wheel there is a wheel cylinder which we will call this Q now this real still in the Q is connected to two pistons b1 and b2 as you can see these two pistons and then pressed against the two brake shoes which we will see other next components what is important to note is the cross sectional area of q is greater than the cross-sectional area of P so you can see that q is a bigger cylinder then P that is the wheel cylinder is greater than the master cylinder next we move on to the next component that is the brake shoes which are touching the piston the brake shoes pressed against the rim of the wheel and finally we have a spring and a spring restores the original position of the brake shoes once you release the brakes so these are the different components and this is the construction of the hydraulic brakes but let’s move on to see what is the working and how these hydraulic brakes use the principle of Pascal’s law so let’s understand Pascal’s principle in terms of the hydraulic brakes now to apply the brakes we know that the first thing we do is apply pressure on the foot pedal so once the foot body is pressed what happens is the piston moves into the master cylinder which means the piston is exerting pressure on the liquid inside the master cylinder now once the liquid is exerted with pressure we know that the liquid inside the master cylinder p will run out from the master cylinder to the wheel cylinder because of the increased pressure now there  is excess pressure in the wheel cylinder but we know pressure gets transmitted equally why because of Pascal’s principle so this increased pressure in the wheel cylinder is going to get transmitted equally to both the Pistons which are b1 and b2 and this is going to make the Pistons that is b1 and b2 push outwards so you can see the increase pressure causes the Pistons to move outwards now if the Pistons move outwards who are they going to press against it is obvious that these pistons will press against the brake shoes which will then press against the rim of the wheel and the motion of the vehicle retards so this is how you apply brakes in hydraulic brakes so this is the first part of the working that is application of the brakes let’s try and understand where this Pascal’s principle fitting inside this Working so to understand that remember that the area of cross section of piston A that is the master cylinder p is less than that of the wheel cylinder q and according to Pascal’s law we know that pressure is transmitted equally so the pressure in the master cylinder is equal to the pressure than the wheel cylinder so we can write P1 equal P2 too but pressure we know its force upon area so we say F1  upon A1 equals F2 upon A2 but we know cross-sectional area of the master cylinder is less than the cross section area of the wheel cylinder and so we write that since a1 is less than a2 it is obvious that f1 must be less than F 2 and therefore F1 upon A1 can be equal to f2 upon a2 only if f 1 less than F to and from this we can see that a small force applied at the foot pedal produces a large force on the piston b1 and b2 off the wheel cylinder Q that is f1 is much less than F2 a small force f1 give you a large force f2 so we have seen how Pascal’s principle is used to apply breaks now let’s see what happens if i want to release the brakes so let’s take a look at the diagram again now in the working of releasing the brakes the first thing of course we do is release the pressure from the foot pedal so you take off your feet from the pedal and the piston is going to come back to its original position now if the piston comes back to its original position it’s obvious that the liquid will run back from the wheel cylinder to the master cylinder the Pistons will come back to the original position and the spring is going to help the brake shoes come back to the original position so the rim of the wheel is now free to move and then we can say that the brakes have been released so we have seen how to release brakes simply by removing your feet from the foot pedal and the pressure causes the liquid to run back in the master cylinder and you can start your car again so this was the working of the hydraulic brake before we conclude our conversation on Pascal’s law that is note the following things in all the three applications we learned we have to be careful that effort is less than load every time the force we applied was much less than the force we obtained that is a small force give us a large force so force applied is less than force obtained which we can say that is effort is less than load also we know that the displacement or we can say the distance moved by effort was greater than the distance moved by load whether it’s the hydraulic press where the bale of cotton moves and larger distance all the hydraulic jack but the car can be moved to a higher height or in this case the hydraulic brake where the Pistons move outwards the displacement or the distance moved by effort was greater than the distance moved by load and therefore we say that the large displacement of the piston causes a small displacement of the load and therefore productive effort and distance moved by effort becomes equal to the product of load and the distance moved by load and the product of any force and the distance is nothing but the work done so from this we can say that the work done by effort becomes equal to the work done by load and so it’s important to remember that in all these applications the work done by effort equal to work done by load also we can say that since effort is less than load we can see that load upon effort is greater than one and therefore mechanical advantage is greater than one also the velocity ratio which is distance moved by effort upon distance move by load will also be greater than 1 and therefore all these machines act like force multipliers so in any case where you require a larger force a force multiplier that is any of these machines are used thank you.