# What is the value of y in this water tank pressure problem?

• foo9008
In summary, the conversation is about finding the value of y in a question related to atmospheric pressure acting on mercury. The person chooses to consider atmospheric pressure as 0 and their working includes the calculation for pressure of water. There is a question about accounting for an extra 1m height and whether to ignore atmospheric pressure. It is clarified that the working should include the extra 1m and the pressure gauge type affects whether atmospheric pressure should be ignored.

## Homework Statement

i am asked to find the value of y in this question . I am not sure should i consider the atmospheric pressure acting on the mercury or not .

## The Attempt at a Solution

i choose to consider the atmospheric pressure as 0 in this case . So , my working is 30000 + (1.5x820x9.81) + (5 x1000x9.81) =13600(9.81)y , where y = 0.68m , am i right ? btw , i am not very sure about whether the pressure of water is (5 x1000x9.81) or not , because the outlet is not at bottom of teh tank , can someone exp;lain pls ?

#### Attachments

• 223.PNG
3.4 KB · Views: 441
If the pipe were even lower than the 1m shown (say 100m lower) would the pressure at the water-mercury interface be affected? So should you account for that 1m height by adding it to the 5m?

Wether you can ignore atmospheric pressure depends on if the pressure gauge is showing absolute pressure or pressure relative to atmospheric ('gauge' pressure).

foo9008
billy_joule said:
If the pipe were even lower than the 1m shown (say 100m lower) would the pressure at the water-mercury interface be affected? So should you account for that 1m height by adding it to the 5m?

Wether you can ignore atmospheric pressure depends on if the pressure gauge is showing absolute pressure or pressure relative to atmospheric ('gauge' pressure).
i think the extra 1m should take into consideration , am i right ? so , the working should be 30000 + (1.5x820x9.81) + (6 x1000x9.81) =13600(9.81)y ?

foo9008 said:
I think the extra 1m should take into consideration , am i right ?
Yes.
So, the working should be 30000 + (1.5x820x9.81) + (6 x1000x9.81) =13600(9.81)y ?
OK if the 30 kPa is gauge pressure.

foo9008

## 1. What is the definition of pressure at a water tank?

The pressure at a water tank is the amount of force exerted per unit area on the walls of the tank by the water inside.

## 2. How is the pressure at a water tank calculated?

The pressure at a water tank is calculated by dividing the weight of the water by the area of the tank. It can also be calculated using the formula P = ρgh, where P is the pressure, ρ is the density of water, g is the acceleration due to gravity, and h is the height of the water column.

## 3. What factors affect the pressure at a water tank?

The pressure at a water tank can be affected by the weight and volume of the water in the tank, the temperature of the water, and the height of the water column.

## 4. How does the pressure at a water tank change when the water level changes?

The pressure at a water tank increases as the water level increases and decreases as the water level decreases. This is because the weight and volume of the water changes, affecting the overall pressure at the bottom of the tank.

## 5. What are the units of measurement for pressure at a water tank?

The most common units of measurement for pressure at a water tank are pounds per square inch (psi) or kilopascals (kPa).