# Homework Help: Fluid Mechanics!

1. Mar 15, 2009

### hank09

1. The problem statement, all variables and given/known data

A submersible with a mass of 2.75 x10^3 kg remains at a constant depth beneath the ocean surface. To make the submersible rise, 1.50 x10^2 kg of ballast is released. Ignoring friction, what is the upward acceleration of the submersible? (D = 1.025 x 10 ^3 kg/m^3 )

2. Relevant equations

Fnet=Fb-Fg
Fb=weight-apparent weight.
Fg/Fb=Density of object/Densitiy of fluid
Fb=mass of fluid x gravity

3. The attempt at a solution
First, I tried using Fnet=Fb-Fg. I multiplied 150x9.81. I thought this would be the buoyant force. Then, i multiplied 2.75 x10^3 kg by 9.81 as well. I subtracted the two values, and then divided the given net force by the sum of two masses. I think my answers are way off. I am so lost. Don't I have to calculate the Fg of the object and then calculate the required acceleration of the buoyant force that will cancel off the Fg?

2. Mar 16, 2009

### tiny-tim

Welcome to PF!

Hi hank09! Welcome to PF!
why?

F = ma, so what is that F?