Questions: Hydraulic Systems in Engineering

Question 1

A hydraulic lift has a small piston with area 10 cm² and a large piston with area 200 cm². If you apply 50 N to the small piston, what force does the large piston produce?

• A. 50 N
• B. 250 N
• C. 1000 N
• D. 10000 N

Answer: (C)

Pressure = 50 N / 10 cm² = 5 N/cm². This pressure acts on the large piston: F = 5 N/cm² × 200 cm² = 1000 N. The mechanical advantage is 200/10 = 20, and 50 × 20 = 1000 N.

Question 2

In a hydraulic system, the small piston moves farther than the large piston.

• T. True
• F. False

Answer: True

Conservation of energy requires that the volume of fluid displaced is the same on both sides. Since the small piston has less area, it must travel a greater distance to displace the same volume. This is the distance-force tradeoff: force is multiplied, but distance is divided.

Question 3

Why do car brakes use hydraulic fluid instead of cables to transmit braking force?

Model answer: Hydraulic fluid transmits pressure equally to all four brake calipers simultaneously, ensures consistent braking force regardless of how the brake lines are routed, and allows force multiplication through different piston sizes. Cables would require complex routing to reach all wheels and would not distribute force as evenly.

Hydraulic brakes also self-adjust, have fewer wear points than cable systems, and provide better feel feedback to the driver. Pascal's principle ensures that the master cylinder pressure reaches all wheel cylinders equally, which is critical for balanced braking.