When the pen drops, the distance to the the ground is 10m
and the pen has an initial speed of 1m/s, equal to the air ballon, direction towards up. Thus, during a short period of time the pen is going up until the speed is 0 for the action of gravity. So, to solve the problem it is necessary to calculate the distance pen went up from the moment the pilot dropped it.
The acceleration of the pen is
The pen reaches the maximum high when