Pascal's Law

When you squeeze an enclosed fluid, the pressure you create pushes out equally in every direction, not just where you pushed it. That means a small force on a small piston can create the same pressure as a much bigger force on a large piston — this is how hydraulic lifts multiply force.

F₂ / F₁ = A₂ / A₁

• F₁ — input force (N): the force pushed down on the small piston
• A₁ — input area (m²): the area of the small piston
• F₂ — output force (N): the force produced at the large piston
• A₂ — output area (m²): the area of the large piston

A hydraulic lift has a small piston with area 0.01 square meters and a large piston with area 0.1 square meters. If you push on the small piston with 10 newtons, how much force appears at the large piston?

• F₁ = 10 N
• A₁ = 0.01 m²
• A₂ = 0.1 m²

1. F₂ = F₁ · (A₂ / A₁)
2. F₂ = 10 N · (0.1 m² / 0.01 m²)

F₂ = 100 N

Using the same lift, if you push on the small piston with 20 N instead, how much force appears at the large piston?

• 200 N
• 20 N
• 2000 N

To lift a heavy car using this hydraulic lift, which piston should you push on to use the least force?

• The large piston, because it has 10 times the area
• The small piston, because it needs less input force
• Either piston — it makes no difference