The physics
Pascal's law: push on a closed liquid, and its pressure rises. It rises by the same amount everywhere in the liquid.
A jack uses this. A small push on a small piston makes a pressure in the oil. The same pressure pushes on a big piston. So the big piston gets a big force.
P = F₁ / A₁ = F₂ / A₂ F₂ = F₁ × A₂ / A₁
Round pistons: the area goes as the diameter squared. Put both areas in one unit. One cm² is 10⁻⁴ m².
A = πd² / 4 F₁ = F₂ (d₁ / d₂)²
The jack gives force, not energy. The small piston moves far, and the big piston moves a little. The work on both sides is the same.
W = F₁ d₁ = F₂ d₂