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 1500 kg ?

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

Answer 1

Answer: (A)

3.75 kg

The 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.