Hydraulics Question (1 Viewer)

[ShrimPeE]

Can anyone please help me with this hydraulics question? I thought the answer was 50 because it acts in ratios... How does this question work?

http://www.members.optusnet.com.au/shrimpee/pics/hydraulics.jpg

 

[Xayma]

Its the ratio of the areas.

You are given the diameter.

The diameter is 5 times bigger, therefore the area is 25 times bigger

 

[Assasinator_2]

Its the ratio of the areas.

You are given the diameter.

The diameter is 5 times bigger, therefore the area is 25 times bigger

This is due to pressure = force * area, thus area is important, as you are balancing the force down on the block, due to gravity (9.81*mass (10kg)) with the force up (pressure/area)

since it's dealing with a liquid, which is (pretty much) uncompressable, you are able to simply use ratios between force down on one side, and force up on the other, wit hrelation to areas of both sides

if it's got a diameter of 20mm, its area is pi*10*10 = 314.16 etc etc
as opposed to 100mm diameter = pi*50*50 = 2500 * 3.1416 = 7850
7850/314.16 = ~25
Therefore, ratio of areas is 25:1

 

[Xayma]

Just on that note, you are normally better off leaving it as π (grr stupid lack of HTML) instead of finding an approximate value as they cancel out, it also makes a few steps easier

 

[ShrimPeE]

Coolz! Thanx heaps =D