Finding the force on a camera window underwater

[yourheartandsoul]

Homework Statement

Deep-sea photographs have been made at depths of 8000 m. (a) What is the pressure at this depth? (b) What is the force on the camera win dow if it measures 0.1 by 0.15 m?

Relevant Equations

P = dgh
F= PA

I figured out that the pressure is 8.0442x10^7 Pa and I’m not sure how to approach the second half of the question.

I’m thinking I use the formula F=PA but I’m realizing it’s not saying that .15m is a diameter or a radius.

 

[kuruman]

It's a 0.1 m × 0.15 m rectangle.

 

[BvU]

And what's on the other side of the window ?

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[yourheartandsoul]

It's a 0.1 m × 0.15 m rectangle.

oh wow I'm on another planet today duh. So i would use the area of a rectangle with the F=PA?

 

[kuruman]

oh wow I'm on another planet today duh. So i would use the area of a rectangle with the F=PA?

Not so fast. To paraphrase @BvU, what's on each side of the window?

 

[DaveC426913]

It is an assumption, but a good one, I think. The inside of the housing will be one atmo of air.

 

[yourheartandsoul]

Not so fast. To paraphrase @BvU, what's on each side of the window?

Water one side and a camera on the other.. lol not too sure what's on the inside of a camera lens. it was for a test so if it was wrong to approach it that way then oh well. I live and learn

 

[kuruman]

It is an assumption, but a good one, I think. The inside of the housing will be one atmo of air.

Assuming, of course, that the person who assembled the camera didn't work under pressure. (Sorry, I had to say that.)

 

[haruspex]

And what's on the other side of the window ?

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It doesn't specify net force, so my guess is they just want the force from the water side.
If it's 1atm inside then the net force will be just ρgd.
Note also it is seawater, not fresh water.

 

[BvU]

It doesn't specify net force, so my guess is they just want the force from the water side.
If it's 1atm inside then the net force will be just ρgd

Fully agree with $\rho\, g\,\Delta h$ -- it's more an awareness thingy

Note also it is seawater, not fresh water.

With 8.0442x10⁷/9.81/8000 = 1025 that seems to be in perfect order ..

 

[haruspex]

Fully agree with $\rho\, g\,\Delta h$ -- it's more an awareness thingy

Let me be clearer - I think the way it is worded implies 1atm +$\rho\, g\,\Delta h$, not that it will make much difference.