State Pascal's law. With a labelled diagram, explain how a hydraulic lift lifts a heavy load with a small force.

1. 1 · State the law. Pressure applied to an enclosed liquid is transmitted undiminished to every point of the liquid and to the walls.
2. 2 · Draw the lift. U-tube with oil; a small piston A₁ with force F₁; a large piston A₂ with a platform, load and force F₂.
3. 3 · Pressure on the small piston. P = F₁/A₁.
4. 4 · Pressure reaches the large piston. By Pascal's law the same P acts on A₂, so F₂ = P × A₂ = F₁ × A₂/A₁.
5. 5 · Explain the gain. A₂ is much larger than A₁, so F₂ is much larger than F₁. The small piston moves farther, since A₁d₁ = A₂d₂.
6. 6 · Real life. Service stations lift cars this way, and buses use the same idea in hydraulic brakes.
7. 7 · Close in one line. The lift multiplies force by A₂/A₁, but it does not multiply work.

Scoring tip: Draw the two pistons clearly different in size and label A₁, A₂, F₁ and F₂. An unlabelled diagram loses the diagram mark.