5. A man falling vertically by parachute in a steady downpour of rain observes that when his speed is v1 the rain appears to make an angle a with the vertical. When his speed is v2 the rain appears to make an angle S with the vertical. Show that the rain actually falls at an angle 0 with the vertical given by (12 marks) (v2 - V1) cot ! = 12 cot a - v1 cot B (0# 0) All angles are measured from the upper vertical. 6. A swimmer at A crosses a river of width 40m which has a uniform current. In crossing the