A balloon of mass m1 falls down. At the moment when the speed of the ball = v0, and the acceleration a0

A balloon of mass m1 falls down. At the moment when the speed of the ball = v0, and the acceleration a0, the ballast m2 was dropped. The drag force of the air is proportional to the speed, the lift is F. How long after that the ball will continue to fall.

Thus, oo dumping ballast, the following formulas will work for us:
m1 * g + m2 * g = F + Fс;
Ac = g * (m1 + m2) – F;
After the reset, the following formulas will work for us:
F + Fc – m1 * g = m1 * a;
a = (F + Fc – m1 * g) / m1;
Thus:
a = v0 / t;
Let’s transform:
t = v0 * m1 / (F + Fc – m1 * g);
Answer: t = v0 * m1 / (F + Fc – m1 * g).