1. Jan 19, 2016

### hotjohn

1. The problem statement, all variables and given/known data
why the pressure gradient is = - 2ρg ? why not ρg ?

2. Relevant equations

3. The attempt at a solution

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2. Jan 19, 2016

### Staff: Mentor

Have you drawn a free body diagram and performed a force balance?

3. Jan 19, 2016

### hotjohn

IMO , it should be -P1 - (P1 +ρg ) .... why the ans is = - 2ρg ?

4. Jan 19, 2016

### Staff: Mentor

I don't see a right hand side to this equation, and one of your two pressure terms is of the wrong sign. Next time you respond, please respond with a complete force balance equation, based on a proper free body diagram, and including a mass times acceleration term.

5. Jan 19, 2016

### hotjohn

so , what is the correct one ?

6. Jan 19, 2016

### Staff: Mentor

No, no. That's not how we work here. We can only help you to help yourself by giving you hints and asking you leading questions. So my first hint for you was to draw a free body diagram showing the forces acting on the water (do you feel that you have progressed beyond the need to use free body diagrams any more?), and my second hint was to write a force balance equation based on the free body diagram. So, the ball is in your court now.