Respuesta :
The Answer is A becuase the piano moving up is is going in a positive way whe it stops the forces are equal then when it falls the forces are negative
Answer:
Option A is correct
Explanation:
As the piano moves upwards, the net force acting on the piano is
Fnet = T - mg
Where T be the tension in the string and mg be the weight of piano.
Here Fnet is always positive because piano is moving up and upward direction is taken as positive.
When the piano stops, the net force acting on the piano is zero.
Fnet = 0
When the piano moves downwards, the net force acting on the piano is
Fnet = mg - T
As the net force is acting downwards, so the direction of force is negative.