Billy stands on a hill without slipping. In which direction is the force of friction acting? A. along the surface of the hill, toward the bottom of the hill.
B. perpendicular to the surface of the hill
C. straight up
D. Along the surface of the hill toward the top of the hill.

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. 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