Pressure and resultant force

  • Thread starter Newton86
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  • #1
Newton86
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Homework Statement



( athmosphere pressure is normal 101 kPa)
A ”tub” has a form as a prism ( like on the pic ) with the following lengths
Length: 2m
Width : 0,75m
height: 0,5m
Whats the absolute pressure agains the sides at the bottom of the “tub” + resultant force

191143.jpe



Homework Equations



I Think
p=po + pgh


The Attempt at a Solution




(Im not sure about po and p )

For the absolute pressure I got :
P=Pa +pgh = 101 + 0,75*9,81*0,5 = 104,67 pa

And the resultant force
P = pgh = Resultantkraft: pgh = 0,75*9,81*0,5 = 3,675 pa
I have done something wrong haven't i ?

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
Newton86
59
0

Homework Statement



( athmosphere pressure is normal 101 kPa)
A ”tub” has a form as a prism ( like on the pic ) with the following lengths
Length: 2m
Width : 0,75m
height: 0,5m
Whats the absolute pressure agains the sides at the bottom of the “tub” + resultant force

191143.jpe



Homework Equations



I Think
p=po + pgh


The Attempt at a Solution




(Im not sure about po and p )

For the absolute pressure I got :
P=Pa +pgh = 101 + 0,75*9,81*0,5 = 104,67 pa

And the resultant force
P = pgh = Resultantkraft: pgh = 0,75*9,81*0,5 = 3,675 pa
I have done something wrong haven't i ?

Someone Please I am beggin here :smile:
 
  • #3
tiny-tim
Science Advisor
Homework Helper
25,838
255
( athmosphere pressure is normal 101 kPa)
A ”tub” has a form as a prism ( like on the pic ) with the following lengths
Length: 2m
Width : 0,75m
height: 0,5m
Whats the absolute pressure agains the sides at the bottom of the “tub” + resultant force

For the absolute pressure I got :
P=Pa +pgh = 101 + 0,75*9,81*0,5 = 104,67 pa

And the resultant force
P = pgh = Resultantkraft: pgh = 0,75*9,81*0,5 = 3,675 pa

Hi Newton86! :smile:

erm … what's the tub filled with? :confused:

and I don't think the width affects the pressure, does it? :smile:
 
  • #4
Newton86
59
0
Hi again Tim:smile::smile:
Its filled with water. And yeah you got a point with the width :tongue:

I think I have it now after I see what pa and P is.

absolute pressure:
Pa +pgh = 101000 + 1000kg/m^3*9,81*0,5 = 105900 pa

101kpa is 101000 pa and 1000kg/m^3 is the density of water.

Resultant force:

Resultantkraft: pgh = 1000kg/m^3*9,81*0,5 = 4900 pa

does this make sense ?
 
  • #5
tiny-tim
Science Advisor
Homework Helper
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Hi Newton86! :smile:

Looks very good! :smile:

(But I don't understand what they mean by "resultant force" … 49000pa is a pressure … pressure = force/area … do they mean resultant-force/area? :confused:)​
 
  • #6
tiny-tim
Science Advisor
Homework Helper
25,838
255
Hi Newton86! :smile:

Looks very good! :smile:

(But I don't understand what they mean by "resultant force" … 49000pa is a pressure … pressure = force/area … do they mean resultant-force/area? :confused:)​
 
  • #7
Newton86
59
0
Dont ask me You are the smart one:wink:
But the resultant force to the bottom of the "tub"
I don't know but we got the information about length and width and so far i haven't used that info, maybe i should :confused:
 
  • #8
tiny-tim
Science Advisor
Homework Helper
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255
Hi Newton86! :smile:

(hmm … sometimes they put in extra information just to test if you know what's relevant)

Is the question asking for the "resultant force at the bottom of the tub", or for the total resultant force on all the sides of the tub, right up to the top?
 
  • #9
Newton86
59
0
"The resultant force agains the bottom of the tub" I would say it also have info about a hatch but I think that is only relevant to the next question who is what the resultant force is agains the hatch..
 

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