Based on the nebular theory, which of these is a step in the formation of the center of a new planetary system? a) evaporation of condensed gases due to heat b) combination of condensed gases due to gravity c) contraction of condensed gases due to nuclear fission d) expansion of condensed gases due to nuclear fission .

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? a. positive force, balanced force, negative force b. negative force, balanced force, positive force c. positive force, unbalanced force, negative force d. negative force, unbalanced force, positive force