A balloon filled with helium gas has an average density of rhob = 0.39 kg/m^3. The density of the air is about rhoa = 1.23 kg/m^3. The volume of the balloon is Vb = 0.066 m^3. The balloon is floating upward with acceleration a. Required:
a. Express the net force F on the balloon in terms of its weight W and the buoyancy force Fb on it, assuming upward is the positive direction.
b. Calculate the numerical value of the acceleration a in m/s^2.