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158 SCIENCEA riddle for youIn some situations, I oppose the motionin other situations, I facilitate the motionbut, I always opposethe relative motionbetween two moving surfaces.Put some lubricant, andI become small there.Make the moving surfaces roughI make the movement tough.I may be%u2014static, sliding or rollingbut whenever two surfaces are in motionI am always there,Tell me who I am!%u00a9 NCERTnot to be republished
