Answer:
Positive force → Balanced force → Negative force.
Step-by-step explanation:
When Diego gives a big lift to the piano with the help of the pulley system at that time, initially piano moves upward. In this case, a positive force was acting on it.
After that, when piano stops, in this condition, a balanced force was acting on it.
After some time, the piano starts falling. Here, the negative force was acting on the piano.
So, from here, we can say that the forces were a positive force, then a balanced force, and in the end, it was a negative force.