help on phsyics?

Question

when a submarine is under water, does the buoyant force depend on the weight of the submarine?

Answer 1

No
Only on the volume of water displaced

Answer 2

Definitely, positively, absolutely NO!
We can calculate buoyancy A using the formula A=d*g*V, where d is the density of the fluid (in this case water), g the acceleration of gravity and V the volume of displaced water. Since d and g are constants, variations in A result only form variations in V. But since the submarine is fully submerged, it displaces a constant volume of water (which is equal to the volume of the submarine itself).
Only when a vessel is parlty under water (rising or sinking) does V change, which means that so does A.

In order for a submarine to maintain its depth (that is: NO rising, No sinking) the weight B of the vessel must be equal is magnitude to A, that is Ftotal = A - B = 0.
What (people in) submarines do in order to sink, is that they flood the vessel's tanks with water in order to make it heavier, so that A A-B < 0 -> Ftotal<0 so the vessel sinks.
In order for the vessel to surface, they empty the water tanks, so B decreases. In this case A>B -> A-B>0 -> Ftotal>0 and the submarines rises to the surface!

Answer 3

Yep.

Buoyant force acts equal and opposite to the weight when the body is neither rising or sinking in the fluid. This follows because if the body is vertically stationary (even though it may be moving horizontally), the sum of all vertical forces has to be exactly zero.

In math talk W - B = 0 for a sub not moving up or down; where W is the sub's weight and B is the water's buoyancy. Thus, as you can see, if we increase the weight in the sub, the buoyancy has to also increase to offset that increased weight.

Same idea for a floating sub...W - B = 0 because the sub is not sinking or riding higher out of the water. So as it takes on provisions pierside, buoyancy goes up to offset the additional weight. There is a point where buoyancy can no longer automatically increase; at which time, the sub begins to sink.

Answer 4

Bouyancy is an upward force. It is dependent of the volume of the water displaced and the water's density. Whether or not a submarine is stable at depth is is dependent on whether its bouyant force is equal to its weight, the downward force. So the answer to your question is no.

Answer 5

Yes, the lighter the submarine (as in volume, like per cubic inch), the more buoyant it is.

Answer 6

Yes