A 1 kg mass is projected down a rough circular track (radius = 2.0 m) placed in vertical plane as shown. The speed of the mass at point A is 3 m/sand at point B, it is 6.0 m/s. How much work is done on the mass between A and B by the force of friction?

Conservation of energy principleKE at A = 12×1.0×3.02 = 4.5 JLoss in PE between A and B =1.0 x l0 x 2 = 20JGain in KE from A to B if there had been no friction = 20JTotal KE at B if there had been no friction= 4.5 + 20 = 24.5 IBut actual KE at B = 12×1.0×62 = 18 JLoss in energy due to friction = 24.5 - l8 = 6.5 J