You need to calculate the amount of buoyant force acting on the balloon. Assume it to be U.
so,
mg/6=U-mg
This gives U=7mg/6
And then, assume mass of water to be added is M.
(M+m)g/6=(M+m)g - U
M=2m/5
a balloon of mass m is found to accelerate up at the rate of g/6. the quantity of water that should be put inside the balloon so that it may accelerate downwards at the rate of g/6 is:
You need to calculate the amount of buoyant force acting on the balloon. Assume it to be U.
so,
mg/6=U-mg
This gives U=7mg/6
And then, assume mass of water to be added is M.
(M+m)g/6=(M+m)g - U
M=2m/5