Question

Name the mechanical machine which is used to lift or compress large loads.
A) hydraulic press
B) hydraulic lifts
C) hydraulic brakes
D) none

Answer 1

In fluid mechanics, according to Pascal’s law, when pressure is exerted on a small area of a confined, incompressible fluid, the pressure will get equally distributed throughout the fluid, in all directions. The working principle of hydraulic machines, which contain incompressible fluid in them, is based on Pascal’s law.

Complete step-by-step answer:
When pressure is exerted at a point in an incompressible fluid, the pressure gets distributed equally and undiminished in all directions of the fluid. This statement is nothing but Pascal’s law or Pascal’s principle in fluid mechanics. Mathematically, Pascal’s law is given by
$\Delta p=\rho g\Delta h$
where
$\Delta p$ is the difference in pressure between two points in an incompressible fluid
$\rho$ is the density of the incompressible fluid
$g$ is the acceleration due to gravity
$\Delta h$ is the difference in elevation between the considered two points inside the incompressible fluid
Hydraulic machines like hydraulic press, hydraulic lifts and hydraulic brakes work according to Pascal’s law. The hydraulic machine used to lift or compress large loads is termed as hydraulic lift.
A hydraulic lift consists of an incompressible fluid, a piston attached to a cylinder, a pump, a tank, a valve and a motor. The motor is used to activate the pump. To move a hydraulic lift upwards, force is exerted on the piston with the cylinder attached to it. This will trigger the motor to pump the incompressible fluid to the cylinder. The fluid experiences a pressure, which is distributed equally and undiminished in all directions. The valve, which connects the cylinder and the lift opens up, and the fluid is allowed to flow to the bottom of the lift. The equally distributed pressure generates a force on the bottom of the lift, which moves the lift upwards. To move the lift downwards, the piston is pulled back, and the reverse process takes place.
Hydraulic lifts are used to carry people as well as goods to the different floors of a multistoried building. These hydraulic machines produce less sound when compared to other types of lifts. Hydraulic lifts are not only used in construction of buildings, but also in other industries such as the automobile industry and transportation industry.

So, the correct answer is “Option B”.

Additional Information: Some examples of hydraulic lifts are mezzanine floor lifts, scissor lifts, carousel lifts and two-post lifts. Mezzanine floor lifts can carry a maximum load of $1000kg$ whereas scissor lifts are used to raise platforms. Carousel lifts are used to improve storage capacity while two-post lifts are used in the automobile industry to lift vehicles.

Note: Students need not get confused with the other options. Hydraulic press is a type of machine press, used in metal formation processes like moulding and punching. On the other hand, hydraulic brakes are used in vehicles to carry out braking mechanisms. Both of these hydraulic machines work according to Pascal's law.