Using spring balances and massed carts, the force of motion in one direction was found, and the force of motion in the opposite direction found. The forces were shown by vectors, with the length and direction of the vector used to show the magnitude and direction of the force. Two equal and opposite forces were applied and no motion was detected in the cart. Other demonstrations were used to show that as an action force was applied to an object, an equal and opposite reaction force was shown. Newton's third law was stated in terms of action and reaction forces. Questions and problems from the end of the chapter completed the class.