# How can I calculate the force and pressure on an object submerged in water?

• ML
In summary, the conversation discusses the buoyancy of an object submerged under 50 meters of water and how it is affected by the pressure and volume of the water. It is mentioned that the buoyancy remains the same as long as the object remains 1m3 in volume, and that the buoyant force is the difference between the mass of water displaced and the mass of the object. An equation to determine the buoyant force is also provided.
ML
I was wondering a couple of things about an object of mass 20kg and volume 1m3 being submerged under say 50 metres of water. Basically I'm looking for the two equations that would help me figure out the force and pressure surrounding the object to make it rise.

similar to that of a fishermans' bhoy being submerged.

The bouyancy should be the same at 50m as it is at the surface, since bouyancy is dependant on the mass of the fluid displaced. Although the pressure being exerted on the sides of the object would be much greater, this would be equally true from all directions, so the extra force pushing up from underneath is the same as the extra force pushing down from above.

But so long as the object remains 1m3 in volume, it will displace 1m3 of water, and the mass of that water will be the same at depth as it is on the surface because despite the great pressure, water doesn't compress (well, not much, anyhow). So the object displaces 1,000kg of water at any depth.

Lurch, have you ever been scuba diving? What you find happens is that the air in the object gets compressed due to the pressure and your buoyancy decreases with depth. IIRC you find that the air in an object will occupy 10/(D + 10) times volume than it will at the surface (where D is the depth).

Quite right, jc. You don't mind if I call you that, do you? Makes me feel like I'm in the movie business.

Anyways, that's why I made a point of it to mention that the object's bouyancy remains the same "So long as the object remains 1m3 in volume". But it's good to reinforce the pointthat if the object gets shrunk by the pressure, it will of course become less bouyant.

It's just that buoyancy is important to scuba divers (I got my advanced PADI qualification this Summer) and when you start to descend you find the deeper you go the faster you go down as you lose buoyancy.

.

I appreciate these replies but i was focusing more on the actual force that the buoy would be capable of pulling upwards or an equation to help me determine it.

Originally posted by ML
I appreciate these replies but i was focusing more on the actual force that the buoy would be capable of pulling upwards or an equation to help me determine it.

The boyuant force is the difference between the mass of water displaced and the mass of the object.

Originally posted by ML
I appreciate these replies but i was focusing more on the actual force that the buoy would be capable of pulling up wards or an equation to help me determine it.

The buoyant force is the difference between the mass of water displaced and the mass of the object.

Your 1 m3 displaces 1000kg of water so experiences buoyant force equivalent to the weight of 1000kg of water B=mg= 9.8x103 N, the body has a weight of 9.8*20N. The difference is the weight required to keep the body submerged.

Last edited:

## 1. What is the equation for force and pressure?

The equation for force and pressure is P = F/A, where P represents pressure, F represents force, and A represents the area over which the force is applied. This equation is known as the pressure formula.

## 2. What are the units for force and pressure?

The units for force are typically measured in Newtons (N), and the units for pressure are typically measured in Pascals (Pa). However, other units such as pounds (lb) and atmospheres (atm) can also be used.

## 3. How are force and pressure related?

Force and pressure are directly related to each other, meaning that as force increases, so does pressure. This can be seen in the pressure formula, where pressure is directly proportional to force and inversely proportional to area.

## 4. How does the area over which force is applied affect pressure?

The larger the area over which force is applied, the lower the pressure will be. This is because the same amount of force is spread out over a larger area, resulting in less pressure. Conversely, a smaller area will result in higher pressure.

## 5. What is the difference between force and pressure?

Force is a measure of the amount of push or pull applied to an object, while pressure is a measure of the force distributed over a specific area. In other words, force is the cause of pressure, while pressure is the effect of force.

• Mechanics
Replies
12
Views
2K
• Mechanics
Replies
15
Views
2K
• Mechanics
Replies
25
Views
5K
• Mechanics
Replies
32
Views
4K
• Mechanics
Replies
12
Views
5K
• Introductory Physics Homework Help
Replies
19
Views
418
• New Member Introductions
Replies
1
Views
131
• Mechanics
Replies
1
Views
2K
• Mechanics
Replies
2
Views
1K
• Mechanics
Replies
7
Views
3K