Calculate Absolute Pressure with P = pgh

In summary, the question is in the diagram i have attached. The Attempt at a Solution is to find absolute pressure using the pressure equation and the rule that is taught to start from the right side.
  • #1
TyErd
299
0

Homework Statement


the question is in the diagram i have attached. basically i have to find absolute pressure

Homework Equations


P = pgh where P is Pressure and p is density


The Attempt at a Solution



1st of all i need to convert 750mm into a pressure? somehow don't know exactly.

the rule i was told is starting from the right side, if it goes down it is subtracted and if it goes up it is added. So in knowing that i did: p_atm - (8 * 0.15 ) - ( 10* 0.05) but i don't know the pressure yet coz i don't know how to calculate. is the rest of the method correct though?
 

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  • #2
Hi TyErd! :smile:
TyErd said:
1st of all i need to convert 750mm into a pressure? somehow don't know exactly.

(you mean 758 :wink:)

758 mm of Hg means the pressure at the bottom of a tube of Hg 758mm high …

so you need to know the density of Hg. :smile:
the rule i was told is starting from the right side, if it goes down it is subtracted and if it goes up it is added. So in knowing that i did: p_atm - (8 * 0.15 ) - ( 10* 0.05) but i don't know the pressure yet coz i don't know how to calculate. is the rest of the method correct though?

Isn't it adding for both of them?

You start with atmospheric https://www.physicsforums.com/library.php?do=view_item&itemid=80" and then it increases when you go down …

don't you have to go down from the interface to that little arrow? :redface:
 
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  • #3
okay i get how to calculate the atmospheric pressure now. According to my book and a couple of questions completed with a teacher, If you are starting from the left, you add as you down and subtract as it goes up. And I think he said if you start from the right side, its add if you up and subtract if you go down. I'm not too sure, I need someone to confirm it that's right or not.
 
  • #4
Hi TyErd! :smile:

Forget left and right.

You start with a place where you already know the pressure (usually because it's atmospheric pressure), then if you go down the pressure goes up (ie you add), and if you go up the pressure goes down (ie you subtract). :wink:
 
  • #5
thanks so much! makes a lot more sense now. you're the man
 

What is the formula for calculating absolute pressure using P = pgh?

The formula for calculating absolute pressure using P = pgh is P = pgh, where P represents absolute pressure, p represents density of the fluid, g represents the acceleration due to gravity, and h represents the depth of the fluid.

What is the difference between absolute pressure and gauge pressure?

Absolute pressure is the total pressure exerted by a fluid, including atmospheric pressure, while gauge pressure is the difference between the absolute pressure and the atmospheric pressure. Gauge pressure is often used in pressure measurements as it is more relevant to the specific situation.

What units are used to measure the variables in the P = pgh formula?

The units used to measure the variables in the P = pgh formula are as follows: P is measured in Pascals (Pa), p is measured in kilograms per cubic meter (kg/m³), g is measured in meters per second squared (m/s²), and h is measured in meters (m).

Can the P = pgh formula be used for any fluid?

Yes, the P = pgh formula can be used for any fluid as long as the units are consistent and the fluid is subject to the same gravitational acceleration. However, the density of the fluid may vary depending on the fluid being measured.

What are some real-world applications of using the P = pgh formula?

The P = pgh formula is commonly used in industries such as engineering, meteorology, and oceanography to measure pressure in liquids and gases. It is also used in barometers to measure atmospheric pressure and in hydraulic systems to calculate pressure changes in fluids.

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