Explanation:
Since the balloon is not accelerating means that the net force on the balloon is zero. This implies that the weight of balloon must be equal to the buoyant force on balloon.
Hence, the buoyant force equals the weight of air displaced by the balloon, also 20,000 N.
Weight of the air displaced = density of air × volume
The density of air at 1 atm pressure and 20º C is 1.2 kg/m³
the volume V = 20,000/(1.2×9.8) = 1700 m³
The power delivered is equal to the product between the voltage V and the current I:

This power is delivered for a total time of

, so the total energy delivered to the battery is
When you drop an object on the moon, it falls to the ground.
But it only falls about 1/6 as fast as it falls on Earth.
This happens in basketball. It is known as "jump ball".