Finding the acceleration of a balloon

[kelsif]

1. An empty spherical weather balloon with a mass of 5 kg has a radius of 2.879 m when fully inflated with helium. It is supposed to carry a small load of instruments having a mass of 10 kg. Taking air and helium to have densities of 1.16 kg/m^3, respectively, what will be the acceleration of the balloon and load immediately after it is released?



2. i have a= v^2/r and Bernoulli's equation P1+.5(pv1^2+pgy1)=P2+.5(pv2^2+pgy2)



3. I keep trying to figure a way to manipulate Bernoulli's equation to solve for v to plug into the first equation but can't get it to work. I also tried solving for escape speed (vesc=the square root of 2GM/R). But that doesn't use the densities. I'm extremely confused at this point.

 

[mgb_phys]

Do you need Bernoulli's equation?
Isn't it simply buoyant force upward and weight down.

Remember immediately after release it has no velocity

 

[kelsif]

no i have bernoulli's equation but i don't know how to solve for the acceleration immediately after release...