Describe an comets origin and orbit?

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

Is a copper wire a conductor or insulator?

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