Explain why
(a) rollers are used for transporting luggage.
(b) metal chains are wrapped on tyres when they run on icy roads.
(c) aeroplanes and car bodies, are made more pointed along their fronts.
(d) talcum powder is put on a carrom-board before a game.
(a)Because rolling friction is smaller then sliding friction,therefore it is easier to transport a bag fitted with rollers.
(b)to increase friction by incresing irregularities so that they donot slip on ice.
(c)This process is known as streamlining,giving a special shape to objects that have to overcome fluid friction,therfore aeroplanes and cars are given this shape so that they can reduce friction.
(d)to reduce friction so that the coins can slide easily over the board,here talcum powder is used as lubricant