Hydraulic pressure dropping bottle

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Main Question or Discussion Point

I am attempting to calculate the pressure at the bottom of a bottle at the moment of impact. I have calculated the force of impact ,but now I am unsure if this will be the same force (approx) applied to the top of the liquid to determine the hydraulic pressure at the bottom of the bottle.
In other words I need to find the hydraulic pressure exerted in a bottle, ( a full bottle that has fallen a certain distance).
If i have a bottle full of liquid of given mass falling a given distance.I can calculate the force at which it impacts. But does this help me find the answer to the above question?
 
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  • #2
stewartcs
Science Advisor
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I am attempting to calculate the pressure at the bottom of a bottle at the moment of impact. I have calculated the force of impact ,but now I am unsure if this will be the same force (approx) applied to the top of the liquid to determine the hydraulic pressure at the bottom of the bottle.
In other words I need to find the hydraulic pressure exerted in a bottle, ( a full bottle that has fallen a certain distance).
If i have a bottle full of liquid of given mass falling a given distance.I can calculate the force at which it impacts. But does this help me find the answer to the above question?
I suppose you could estimate it by simply dividing the force by the area of the bottom of the bottle. This makes the assumption that the force is distributed evenly across the bottom and the fluid is in contact with the bottom of the bottle at impact.

CS
 
  • #3
RonL
Gold Member
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It would seem to me that the sum of both masses, (bottle and liquid) will make up the total impact at point of outside contact. The liquid inside will gain energy in the fall, but being a liquid will spread it's energy at impact to the inside bottom and all around the inside walls of the bottle, also the gas portion above the liquid would recieve some of the energy through compression.

Just don't ask me to do any math:biggrin:

Ron
 
  • #4
According to pascals principle.. The pressure applied to the top of the fluid can be calculated by using...... (P1 being a force pushing down on the top of the liquid)

p1= Force1/area1... The pressure on the bottom of the bottle p2=p1+static fluid pressure.. and finally the force on the bottom of the bottle F2 = P2 A2. so I still don't know if the calculation of the force at which the bottle hits is relevant to calculating the above or is there another way to do this.
 
  • #5
stewartcs
Science Advisor
2,177
3
According to pascals principle.. The pressure applied to the top of the fluid can be calculated by using...... (P1 being a force pushing down on the top of the liquid)

p1= Force1/area1... The pressure on the bottom of the bottle p2=p1+static fluid pressure.. and finally the force on the bottom of the bottle F2 = P2 A2. so I still don't know if the calculation of the force at which the bottle hits is relevant to calculating the above or is there another way to do this.
Draw a FBD and sum the forces. Then calculated the pressure. There will be a small hydrostatic head pressure plus whatever pressure is generated by the impact force. The hydrostatic head is probably negligible compared to the equivalent impact pressure so you can probably just ignore it. P1 is on the top of the bottle (atmospheric) and on the bottom so it cancels out...ignore it too.

CS
 

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