Question

In a hydraulic lift, used at a service station the radius of the large and small piston are in the ratio of $20:1$. What weight placed on the small piston will be sufficient to lift a car of mass $1500kg$ ?

• A. $3.75kg$
• B. $37.5kg$
• C. $7.5kg$
• D. $75kg$

Answer 1

The correct option is A $3.75kg$

Answer is A.
Pressure is the amount of force acting per unit area. That is, $P=F/A$.
where:
$p$ is the pressure,
$F$ is the normal force,
$A$ is the area of the surface on contact. Let us consider A = $\pi r^2$.
Therefore, $\frac{F_1}{{\pi r_1}^2}=\frac{F_2}{{\pi r_2}^2}$.
In this case, $\frac{1500}{{20}^2}=\frac{W}{1^2},W=3.75kg.$
Hence, weight to be placed on the small piston sufficient to lift a car of mass 1500 kg is 3.75 kg.