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A homework problem states:

An aquarium 5 ft long, 2ft wide, and 3ft deep is full of water. Part C: find the hydrostatic force on one end of the aquarium.

Questions (I've completed part a and b. B asked for the force on the bottom which was 1875 lbs.:

  1. What exactly does one end of the aquarium mean?

  2. Is there a standard to applying long and wide in mathematics problems? It may not matter in calculating area, but in other instances it might. For example, calculating the area of a vertical standing slice would either have to be 2dx or 5dx.

  3. My solutions manual shows that part C requires setting up an integral with a range from 0 to 3. This means that the "one end" of the aquarium is the top side? How else could the range be 0 to 3?

Here's my drawing of the aquarium: alt text

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Btw, the solutions manual solution to C is: Integral density*depth*2dx from 0 to 3. Which is Integral 62.5x * 2dx from 0 to 3. Why is the depth variable? I keep thinking "one end" means one side of the tank. Apparently, not.... –  ShrimpCrackers Nov 21 '10 at 2:35
    
1. Objects are assumed to be longer than they are wide (unless a front and back are explicitly specified). –  trutheality Nov 21 '10 at 2:36
    
2. You integrate over depth to get the force onto one side because at each horizontal cros-section the pressure is different (since it's a function of depth). –  trutheality Nov 21 '10 at 2:38
    
trutheality. Thanks. Makes sense now. Add a formal reply and I can accept your answer for points. –  ShrimpCrackers Nov 21 '10 at 2:46
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  1. Objects are assumed to be longer than they are wide (unless a front and back are explicitly specified).

  2. You integrate over depth to get the force onto one side because at each horizontal cros-section the pressure is different (since it's a function of depth).

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