The class was started by reviewing the answers to the homework questions. The airplane problem presented on Wed. was discussed and the forces acting on the plane outlined. The forward force was introduced as thrust and the opposite force as the friction due to air. In equilibrium, the sum of both forces equal zero. The measurement of the weight in Newton of a mass suspended from a single spring balance was compared to the Newtons measured in each of 2 spring balances attached. Each balance indicated 1/2 the weight of the mass. The weight in each balance was compared to the single total as the balances were spread and the angle increased. It was shown that the forces increased on the rope attached to the mass and springs as the angle increased. A vector diagram to determine the resultant force when the forces were equal was drawn and a parallelogram square completed.The resultant force was shown to be equal to the square root of 2 x one of side forces. How to determine the resultant force when the two forces are not equal was presented as the problem to be solved on Monday. Test on chapter 2 next week, day to be determined in advance...