A 70kg student is 120m above the ground, moving upward at 3.5m/s, while hanging

Question

A 70kg student is 120m above the ground, moving upward at 3.5m/s, while hanging from a rope, hanging from a 280kg helium balloon. The lift on the balloon due to the buoyant force is 3000 N. How long does it take the balloon to stop rising?

Side note: I am given a blank motion diagram, blank mortion information table, and a blank body diagram that I can fill in to help me solve the problem.

My issue is not understanding which formulas to use and why. I don't even know where to start. Please help to explain

Explanation / Answer

Mainly two forces act on a floating balloon. That's, the weight(mass*acceleration due to gravity) and the buoyant force. While the former acts in downward direction, the later acts in the upward direction.

Now according to the problem, the buoyant force on the helium balloon has to be nullified by its weight plus the weight of the person. Then only the balloon will stop rising.

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