Physics · Mechanical Properties Of Fluids · NEET
No. The output force is larger, but the big piston moves a much smaller distance. Work stays the same: F1 x d1 = F2 x d2. If force is multiplied 50 times, the distance moved is 1/50 as much. Energy is only transferred, never created.
Pascal's law says the pressure applied to an enclosed liquid is transmitted equally everywhere. So P is the same at both pistons. But force = pressure x area (F = P x A). The big piston has a larger area A2, so the same pressure gives a larger force. Same P, bigger A, bigger F.
Since pressure is equal: F1/A1 = F2/A2. So the output force is F2 = F1 x (A2/A1). For circular pistons the area ratio is (r2/r1) squared, so a piston with twice the radius gives 4 times the force.
Both use Pascal's law. In a lift the goal is a big force to raise a load, so A2 is much larger than A1. In brakes, you press one master piston and the pressure reaches all four wheel pistons equally at the same time, so all wheels brake together and evenly. The main idea in brakes is equal transmission to all wheels.
Yes, the liquid must be nearly incompressible so pressure passes on without being wasted in squeezing the fluid. Oil (a liquid) is used, not air, because a gas compresses easily and would soak up the pressure like a spring, making braking spongy and slow.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Pascal's law: pressure applied to an enclosed, incompressible liquid is transmitted equally and undiminished to every point of the liquid and to the walls of the container.
The output force is 4 times the input force, because F2 = F1 x (A2/A1) and A2/A1 = 4. But the big piston rises only 1/4 as far.
Because pressure reaches all four wheel pistons equally at the same moment, all wheels get the same braking effort, giving smooth and balanced stopping.
It should not for lifts and brakes. Gases compress easily, so much of the applied pressure would be lost compressing the gas. An almost incompressible liquid transmits pressure fully.
If a 10 N force is applied on a piston of area 0.001 m2, pressure P = 10/0.001 = 10000 Pa. On a larger piston of area 0.05 m2, force = P x A = 10000 x 0.05 = 500 N. So 10 N lifts 500 N.
