physics

[shaq786]

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For those that are still going to take the mcat or still want to do more questions:

In a given system of ideal fluid flow, the fluid has a greater velocity at point A than at point B. Compared to point B, point A must also have a:

a. lower fluid temperature
b. higher fluid pressure
c. greater cross-sectional area of flow
d. greater volume flow rate

Can anyone find a good explanation

 

[tank you]

Isn't that from the examkrackers website? I think if you go into the forums there, someone has an explanation for it.

 

[DaveinDallas]

Bernoulli's equation, isn't it? See, I'm already erasing traumatic memories....

 

[aug14]

For those that are still going to take the mcat or still want to do more questions:

In a given system of ideal fluid flow, the fluid has a greater velocity at point A than at point B. Compared to point B, point A must also have a:

a. lower fluid temperature
b. higher fluid pressure
c. greater cross-sectional area of flow
d. greater volume flow rate

Can anyone find a good explanation

I think its 'a' - but only because I dont think its b,c or d. Its not 'b' because greater velocity goes with lower presure. Its not c because greater cross sectional area would go with the slower velocity. Its not d because volume flow rate should be the same everywhere. With that said, I am still not sure of 'a' because I never heard of a relationship between velocity and temperature for fluids. Does your question give any more information? What type of system is it? If its not a isolated system, then choice 'd' would be possible.

 

[MDtoBe777]

I agree with Aug 14. All areas throughout a pipe have the same volume flow rate (A*v). Therefore, it doesn't matter that the velocity is greater in one area or another...the flow rate will be the same when assuming ideal flow. Also, it can't be b cuz that is the opposite choice. C is also the opposite choice.

I'm going with A.

 

[aug14]

It's d. Velocity is a rate too, so volume flow must be greater. Temperature is irrelevent. c would be correct if it were "less"

vA = constant, so how could it be 'd' ?
v = velocity
A = cross section area

Assuming constant density, the product vA must be the same everywhere, or else you would violate the conservation of mass principle.

 

[shaq786]

Yea it is A....It felt like I was trying to develop a brand new theory trying to explain it to myself.

Its from EK's website so I guess i'll go check up on the detailed solution over there.

thanks guys.

 

[Ajay]

What's the official explanation?

 

[shaq786]

I checked on the site, but it didnt have one and I know were not allowed to use the ideal gas equation for liquids. Oh well.

 

[dchan5]

i agree with A and I also reasoned the same as you guys.....I have an idea, not sure if it's correct about why the temperature is lower..here goes:

since a fluid can also be a gas, we can replace the density with the ideal gas equation rho = PM/RT..plug it in and the pressure cancels out leaving RT/M for the pressure term of Bernouli's...Then we can reasoin that if velocity_A > velocity_B, then T_A < T_B.

That's my best guess.