# Homework Help: Force problem

1. May 10, 2006

### whoknows123

I tried this for two nights and it doesnt make sense to me because my teacher did not go over it.

The bottom of the Mariana Trench, located in the Pacific Ocean, is about 11,000 m below the ocean's surface. If an underwater vehicle were exploring the region, at the depth of 10650 m,

a) what force would the water exert on the vehicle's circular winder, which has a radius of 0.2 m? ___N

b) The mass of a jetliner is 1.2 X 10^5 kg. Please fill in the following relationship:
the force on the window is as much as the weight of _______ jetliners.

Thanks a bunch.

2. May 10, 2006

### Andrew Mason

What is the pressure (Force/area) at 10650 m of water? (ie. how much does a column of water 1 m square weigh?). What is the area of the window?

I think they mean the window of the underwater vehicle, not the jetliner, so use the answer in a) and compare it to the weight of 1.2x10^5 kg.

AM

Last edited: May 10, 2006
3. May 10, 2006

### whoknows123

nothing else is given except for what I wrote and density of salt water = 1025 kg/m^3

4. May 10, 2006

### whoknows123

i'm just wondering what equations to use because in my mind, this problem is confusing to me.

5. May 10, 2006

### Andrew Mason

The only equation you need is F = ma (where a = g). That and P = F/A (Force/Area). Do you know how to determine the weight of a column of water 10650 m high and 1 m square? That is all you need.

AM

6. May 10, 2006

### Andrew Mason

So how many kg in 10650 cubic metres of salt water? How much does that weigh? So what is the pressure? What is the area of the window? So what is the force?

AM

7. May 10, 2006

### whoknows123

i thought i would have to find pressure at depth and use the radius in some kind of way, I'm a little confused at what your saying

8. May 11, 2006

### Andrew Mason

How do you find force on a window of Area A, at a particular pressure? What does pressure mean?

AM