TBR: Fluids Flow and Pressure

[justadream]

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TBR Physics II page 99

TBR says that a toilet uses a siphon and that "in order to have water flow from the intake end to the output end, there must be a net pressure difference, where the gauge pressure is greater at the output end"

Can someone explain the bolded? Why does pressure have to be greater at the output end? This is not intuitive to me.

For example, lets say you have 2 adjacent rooms at different pressures (e.g., 1 ATM, 1.1 ATM). When you open the door between the rooms, doesn't air flow from high to LOW pressure?

 

[mehc012]

TBR Physics II page 99

TBR says that a toilet uses a siphon and that "in order to have water flow from the intake end to the output end, there must be a net pressure difference, where the gauge pressure is greater at the output end"

Can someone explain the bolded? Why does pressure have to be greater at the output end? This is not intuitive to me.

For example, lets say you have 2 adjacent rooms at different pressures (e.g., 1 ATM, 1.1 ATM). When you open the door between the rooms, doesn't air flow from high to LOW pressure?

This is and always has been a horribly worded answer explanation. Your understanding of the 2 adjacent rooms scenario is correct. You can warp TBR's explanation around until it becomes clear that they were trying to say the same thing (but doing so badly), but having done so myself when reviewing that problem, trust me, it's not worth the mental effort.