How does a little 50 lb tool lift a 900 lb object with just a few light pumps?
In: Physics
Youtubing a video of “how a hydraulic jack works” is probably going to be clearer than reddit can explain in text. However, I shall try.
First, when you push down on that lever, it amplifies how much force is applied to the lever’s piston at the base of the lever arm, which only moves a tiny amount to compensate. So if you apply 10 lbs of pressure on the handle, and move 20 inches, the piston at the base of that lever will only move 2 inches, but apply 100lbs of force. (numbers are approximate, its the relationship that counts.) Now here comes the part you can’t readily see. There’s hydraulic fluid underneath that small piston attached at the base of the lever. When that piston moves, it shoves that hydraulic fluid into the large cylinder that has a large cylinder to match. It’s shoved in there with just as much pressure. So you’re pushing on the small piston with say 100 lbs of force. There’s a piston in the large cylinder that’s connected to the actual jacking shaft, and it’s about 10x as large as the small piston. So with just as much pressure (force over area) with 10x the area, you’ll amplify the force of the small piston by 10, but again loose travel to compensate. 10lbs and 20 inches on the handle, 100lbs and 2 inches at the small piston, means you get about 1000 lbs of force and 0.2 inches out of the jack as a whole. 100x as much as you put in, but you move the lever 100 times further than the jack actually moves.
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