hydraulic

Everyday

1. Worked by the pressure of a liquid, usually oil or water, pushed through pipes. tree →
2. To do with moving water, for example in dams, canals and pipes: hydraulic engineering. tree →
3. (of cement) Able to set hard under water. tree →

In the lessons

In science and design-technology lessons, hydraulic systems show how a small push on liquid in a narrow pipe can make a big force in a wide pipe — this is how car brakes, diggers, car lifts and dentists' chairs work. Children build hydraulic models with syringes and water. Phrases: hydraulic lift, hydraulic brakes, hydraulic arm, hydraulic press, hydraulic pump.

Examples

• The digger's hydraulic arm lifted the heavy rocks. tree →
• We made a hydraulic robot arm using syringes and coloured water. tree →
• The mechanic raised the car on a hydraulic lift. tree →
• Cars stop using hydraulic brakes. tree →
• The dentist's chair moves up with a hydraulic pump. tree →
• A hydraulic press can squash a can flat. tree →
• The engineer studied hydraulics to design the dam. tree →

Note

«Hydraulic» is an adjective; «hydraulics» is the noun for the subject. Compare «pneumatic» — worked by air or gas pressure instead of liquid. The idea: liquids are very hard to squash, so pressure passes through them. In maths/science, pressure = force ÷ area, so a bigger piston gets a bigger force from the same pressure.