- #1

helppls

## Homework Statement

A uniform U-tube is partially filled with water (ρH20 = 1000 kg/m3). Oil, of density 750 kg/m3, is poured into the right arm until the water level in the left arm rises 30 mm. The length of the oil column is then: (Answer:

**40mm**)

## Homework Equations

P = pgh

Pressure = density x gravity x height

## The Attempt at a Solution

Hi, I originally calculated this with a displacement of 30mm and calculated the correct answer (40mm), but when I re-did my FBD I found that the displacement should be 60mm because the water goes up 30mm on the LHS and down 30mm on the RHS, so my answer of

**80mm**was incorrect. The teacher has said that the question is very clear about the displacement being 30mm. Can you please explain why?

H H20 = 30+30 = 60mm = h1

pH20 = 1000 kg/m^3

PH20 = pH20 * h1

H Oil = h2 = ?

pOil = 750 kh/m^3

POil = pOil * h2

Ph20 = POil

rearrange to get

h2 = (pH20 * h1 )/ pOil

= (1000 * 60)/750 = 80mm = height of oil

but the answer is 40mm because a displacement of 30mm should be used?