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 force

Explanation:

Step1: Analyze upward - moving phase

When Diego gives a big lift to the piano and it moves upward, the force applied by Diego through the pulley system is greater than the force of gravity. Since the direction of gravity is negative and the upward - moving force is in the opposite direction, it is a positive force.

Step2: Analyze stopping phase

When the piano stops, the upward - pulling force and the force of gravity are equal. This is a state of balanced forces.

Step3: Analyze falling phase

When the piano starts to fall to the ground, the force of gravity (negative) is greater than any upward - acting force (which may be negligible at this point), so it is a negative force.

Answer:

positive force → balanced force → negative force