On August 12, 2000, the Russian submarine Kursk sank to the bottom of the sea, 350 feet below the surface. The density of water is 62.4 lb/ft^3.

(a) Find the water pressure in pounds per square foot at the depth of the Kursk.

(b) Find the force on a 5 foot square metal sheet held horizontally at the depth of the Kursk.

Find the force on a 5 foot square metal sheet held vertically at the depth of the Kursk. (The bottom of the sheet is at a depth of 350 feet.)

Question

On August 12, 2000, the Russian submarine Kursk sank to the bottom of the sea, 350 feet below the surface. The density of water is 62.4 lb/ft^3.

(a) Find the water pressure in pounds per square foot at the depth of the Kursk.
 

(b) Find the force on a 5 foot square metal sheet held horizontally at the depth of the Kursk.

Find the force on a 5 foot square metal sheet held vertically at the depth of the Kursk. (The bottom of the sheet is at a depth of 350 feet.)

anonymous · Answer

For (a) you need to multiply the density with the depth to get the water pressure at that depth

anonymous · Answer

I just need part B :)

anonymous · Answer

So force = pressure x Area right?

anonymous · Answer

Correct

anonymous · Answer

you know the pressure, and the area

anonymous · Answer

when it is horizontal the area = 5

anonymous · Answer

So for part B it is just the pressure from part a times 5?

anonymous · Answer

yup for the horizontal part

anonymous · Answer

I just need the vertical part

anonymous · Answer

So if it is held vertically what will be its horizontal area?

anonymous · Answer

The same?

anonymous · Answer

nope zero right?

agent0smith · Answer

Imagine looking at the sheet when it's horizontal... then turning it vertical so the edge faces you. What area do you see?

anonymous · Answer

Zero because it is vertical not horizontal

anonymous · Answer

yes!

anonymous · Answer

Okay so the answer is zero?

anonymous · Answer

yup

anonymous · Answer

It says zero is wrong...

agent0smith · Answer

Yeah i wasn't sure it was zero... i think it's because pressure essentially acts in all directions underwater... except from below really. But the sides it would act on.

anonymous · Answer

So shouldn't it be the integral from 0 to 350 of the area of the square?

agent0smith · Answer

Think of a ball in water  - the water pushes on the sides because the water is essentially trying to fill the space that the ball takes up.

anonymous · Answer

So if you considering the horizontal pressure also then you need to integrate it along the height of the square

agent0smith · Answer

0 to 350? The sheet is only 5 ft wide.

anonymous · Answer

It is 350 feet deep

anonymous · Answer

Ya 350 ft is the bottom most point of the sheet, what is the dept at the top of the sheet?

anonymous · Answer

It says it is at the depth of the Kursk so it is at 350 feet at the bottom of the square and at the top 348 below

anonymous · Answer

at the top is it 348 or (350-5)?

anonymous · Answer

I mean 345

anonymous · Answer

yup

anonymous · Answer

So...?

agent0smith · Answer

this might help if you're in calculus http://tutorial.math.lamar.edu/Classes/CalcII/HydrostaticPressure.aspx

anonymous · Answer

Guys I just need the answer to the vertical force, thats all

anonymous · Answer

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