Questions: Pascal's Principle

Question 1

In a hydraulic lift, a 10 N force is applied to a piston with area 0.01 m². The other piston has an area of 0.1 m². What force does the large piston exert?

• A. 10 N
• B. 100 N
• C. 1 N
• D. 1,000 N

Answer: (B)

Pressure = F/A = 10/0.01 = 1,000 Pa. This pressure acts on the large piston: F = P × A = 1,000 × 0.1 = 100 N. The force is multiplied by the ratio of the areas (10:1).

Question 2

A hydraulic system can multiply force without multiplying energy.

• T. True
• F. False

Answer: True

The system multiplies force but the small piston must travel a proportionally greater distance. Work in = work out (F₁ × d₁ = F₂ × d₂), so energy is conserved.

Question 3

Why are liquids used instead of gases in most hydraulic systems?

Model answer: Liquids are nearly incompressible, so when pressure is applied, the force is transmitted almost instantly and without loss. Gases compress under pressure, making the system spongy and less responsive.

If a gas were used, pressing the small piston would first compress the gas before transmitting force, wasting energy and making the system feel soft and imprecise.