# EK #4 C/P #14

#### akimhaneul

2+ Year Member

So I looked it up in my textbook and it says for this kind of problem, the rate of flow through the container is negligible compared to the rate of flow through hole. Can you really assume this?

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#### aldol16

5+ Year Member
The fluid particles are falling from the same height in both instances so their velocities must be the same. The volumetric flow rate is different but this is talking about velocity. That's my interpretation.

#### akimhaneul

2+ Year Member
The fluid particles are falling from the same height in both instances so their velocities must be the same. The volumetric flow rate is different but this is talking about velocity. That's my interpretation.

Thanks. I think I tried to solve this problem using av=av but I guess this doesn't work here since you have to take account of height?

As in since one hole is bigger than the other, the velocity would be slower there

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2+ Year Member
V= SQRT(2gh)

#### aldol16

5+ Year Member
Thanks. I think I tried to solve this problem using av=av but I guess this doesn't work here since you have to take account of height?

Well, av = av means that volumetric flow rates are equal but that makes no sense in this case.

#### akimhaneul

2+ Year Member
Well, av = av means that volumetric flow rates are equal but that makes no sense in this case.

Sorry but I feel like I still don't understand. Can you please explain?

I feel like I'm confused about when to apply bernoullis equation vs continuity equation.

Edit : Oh wait is the volume flow rate different for the two systems because the area of the holes are different? Hence you can't use av=av like I did?

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#### aldol16

5+ Year Member
Edit : Oh wait is the volume flow rate different for the two systems because the area of the holes are different? Hence you can't use av=av like I did?

Exactly. Just think about it from a common sense standpoint. You have two water containers, both at the same height above the ground. You cut a hole at the bottom of each one, one large and one small, at the same time. Which container will empty first? Since the larger hole will lead to more fluid egress per unit time, you know that the volumetric flow rate for that container is different from that of the other one and therefore av does not equal av. A1*V1 = A2*V2 usually applies when you're talking about two sections of a rigid pipe, where the volume flow rate must be equal for the pipe (what goes in must come out).

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