27.A magnetic compass needle oscillates 30 times per minute at a place where the dip is = B 53 and 40 times per minute where the dip is 82 = 37. If B and B are respectively the total magnetic field due to earth at the two places, then the ratio 1 is (Use cos 370 = 0.8) B2 28. An object is placed in between two plane mirrors as shown in figure. Total number of image formed is 10 20 29.A small particle is released from the top of a smooth inclined plane ABC. The angle of the incline suddenly changes from 60 to 30 at point B. Assume that collision between the particle and the incline is totally inelastic. Find the speed (in m/s) of the particle when it reaches the bottom C of the incline. (Take g = 10 m/s) 5 m 7.5 m 60% B 30% C