13. 14. 15. 16. 17. 18. 19. 20. In an isolated system, momentum is not always conserved during a collision. The impulse is always in the same direction as the net force. Kinetic energy is a vector quantity. The change in gravitational potential energy can never have a negative value. The maximum work a force can do on an object occurs when the force is parallel to the direction of motion. Positive work is done when the force and the displacement are in the same directions. To raise a 2.3 kg mass from its resting place on a table, more work is done by lifting it diagonally than lifting it straight up. When you triple the velocity of an object of constant mass, you also triple the momentum