Lifting an elephant with hydraulics

  • #1
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Hey guys, I'm a super amateur at physics, but I occasionally like to calculate random problems that pop into my head.

Today I was thinking about pascal and hydraulics, and wondered if I could devise a (hypothetical) hydraulic system that would allow my weight to lift an elephant.

I want to see if this is correct... or way off...

I figured I could use Pascals idea that the ratio of Area (in) / Area (out) would be equal to Force (in) / Force (out)


Total back of a napkin calculation but.... I researched an elephants weight to be 6000kg (or 60,000 N) - African elephant of course...

My weights about 80 kg (800 N)

The rough area of the platform an elephant could fit on is 3m x 2m (6m^2)

Feeding this into my equation I got that I would need my side of the piston to be about 0.08 m^2 for my weight to equal the elephants.

Could this be achieved by having a platform I stand on (that is the same area as my feet together) which is then attached to a 0.08m^2 piston... or does it not work that way...


Also, if anyone can explain why this whole thing works on a deeper level - like conservation laws and all that, I'd be really curious, as I find this whole system really counter intuitive.

Thanks guys!
 

Answers and Replies

  • #2
Nugatory
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Your numbers are about right (but next time you take on a thought experiment like this, either assume an 8000 kg elephant or plan on sticking 20 kg of lead in your pockets, because 100:1 is easier to calculate with than 75:1). There may be practical problems in building a two-meter by three-meter hydraulic cylinder, but the idea is sound in principle.

To lift the elephant one centimeter you will have to push your platform down 75 centimeters; this follows because the volume of fluid pushed into the chamber under the elephant will be equal to the volume of fluid displaced from the chamber under you. Thus, you will be exerting a smaller force over a longer distance, just as if you were using a long lever to lift the elephant.
 
  • #3
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Thanks! Glad I wasn't totally of the mark. Yup, that's the part that wasn't making sense to me re displacing equal volume of water. 75 cm to go up 1 cm for the elephant makes a lot of sense though

Thanks for your help :)
 
  • #4
CWatters
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This is basically how a hydraulic car jack works.
 

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