A horizontal bar with a mass m suspended from one end is held by a cord with tension T, fastened at a distance D from the end of the bar that is attached to a wall with a frictionless pin. What is the torque about the pin exerted on the bar by the cord?

Light traveling in water, nwater = 1.33, strikes a plastic block at an angle of incidence of 51.4°; part of the beam is reflected and part is refracted. if the index of refraction of the plastic is 2.0, what is the angle made by the reflected and refracted beams?