Explain the Newton's Third Law.
The famous horse and cart physics scenario is described. This scenario is used to describe why many people have a common misconception about what Newton's Third Law says and does not say. Utilize this scenario to describe how people try to argue that no object should move if Newton's Third Law and Second Law were correct (i.e. if all forces have an equal and opposite force, then there will be no net force and if there is no net force then no objects should move). First write out the confused logic the horse uses. Second, write out the correct logic. Finally, explain the importance of external forces acting on a system (in this case the external forces acting on cart and horse).
• What is the logic horse uses?
• What is the horse stating incorrectly?
• What are the external forces acting on horse and cart.