Volume flow rate question

[Lindsey Freeman]

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"Increasing the cross sectional radius of a pipe would have what effect?"
Answer: Flow speed would decrease

Following f=A*v, this answer makes sense to me only if we are assuming that f stays constant. Why do we assume this? In other words, why isn't the answer "volume flow rate would increase"?

Thanks for any help, guys. T-minus 11 days til my test!

 

[Teleologist]

f is volume flow rate and I would think that the volume of fluid going into a hose goes back out the hose; i.e. the hose isn't a black hole.

 

[SuperSneaky24]

In an open pipe system, we assume flow rate is constant. However, the flow velocity will change. Therefore, via the equation A1v1=A2v2, we see that increasing the cross sectional area will decrease the flow velocity.

 

[Teleologist]

In an open pipe system, we assume flow rate is constant. However, the flow velocity will change. Therefore, via the equation A1v1=A2v2, we see that increasing the cross sectional area will decrease the flow velocity.

Volume flow rate is constant. Careful with the wording there. People mistake rate for velocity (a specific rate).

 

[Lindsey Freeman]

Got it - I think I was just confused about this because it is not so in blood vessels, but I'm realizing how this is very different than a pipe open on both ends in a physics problem. Thanks everyone!