Question

Diego is trying to lift a piano to the second floor of his house. Diego uses a pulley system and gives a big lift to the piano.The piano moves upward, then stops, and then it starts to fall to the ground. (The direction of the force of gravity is negative.)

Which list best describes the forces on the piano in the proper order?

positive force → balanced force → negative force
negative force → balanced force → positive force
positive force → unbalanced force → negative force
negative force → unbalanced force → positive forc

Answer 1

positive force → balanced force → negative force.

Reason: Diego first exerts an upward force greater than gravity (net positive) so the piano rises. At the instant it stops the upward force equals the weight (net zero), and then the upward force drops below the weight so the net force is downward (negative) and it falls.