Which of the following statements best summarizes the law of conservation
of energy before and after a change in a system?

Explain vector addition, triangle method and parallelogram method

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

How are the crust and the inner core alike? a) they are both solid. b) they both have the same temperature. c) they are both under the same pressure. d) they are both very close to the center of the earth.