Explain why a swing will not stay in motion forever after you have given it a push. What happens to the mechanical energy of the swing?

Explanation:

As the pendulum swings back and forth, the balance between the two types of energy changes constantly. At some points in its swing, the pendulum has more kinetic energy. At other points, it has more potential energy. ... No pendulum can swing forever because the system loses energy on account of friction.

the correct answer is c   with the systems

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.