7. A light rod is supported horizontally at the two points C and RC RD D. Forces of magnitude 1 N and 2 N are applied vertically to the rod, while a force of magnitude 20 N is applied at an acute angle of 0 to the rod, as shown in the diagram to the right. 2 N 20 N D The rod is on the point of tilting about D. 3 m 1 m 2 m 1 m a) Find the angle 0. [4] b) A mass of 1.5 kg is added to the left-hand end of the rod and, at the same time, the angle O is changed, but remains acute. The rod is now on the point of tilting about C. Find the new angle 0 to 3 significant figures. You should take g = 9.8 m s 2. [5]