The hydraulic jack
When a wheel has to come off, one side of a vehicle is raised with a jack. The kind most widely used is the hydraulic jack.
Figure to be added
What operates here, just as in the hoist, is the transmission of pressure through a fluid. Here too the force is applied to a small piston. The pressure it produces is transmitted through the oil in the jack to a large piston, and the large piston lifts one side of the vehicle.
The hoist and the jack
| Point | The hoist | The jack |
|---|---|---|
| Principle | transmission of pressure | transmission of pressure |
| What it lifts | the whole vehicle | one side of it only |
| Where it lives | fixed at a service station | carried with you |
One idea inside both
The hoist and the jack look quite different, but the same idea is at work in each — a force applied to a small piston produces a pressure, the oil transmits it, and it emerges at a large piston as a large force.