The bowlers rub the ball in his trousers due to reduce/increse friction?
Answers
UR ANSWER:-
When the bowling team gets a ball, it is even on both the sides. The bowling side chooses a side of the ball to rub, and throughout the match they rub only one side of the ball. This rubbing makes the ball shiny on one side. The other side is untouched, so due to wear while playing both the sides are now unequal. One side is shiny and the other is rough. When a fast bowler pitches the ball seam up then the air flows unequally around the ball, due to one side being smooth. This is how the ball starts swinging.
You would have observed the spin bowlers and fast bowlers rubbing the ball with their pants or towels when they bowl at night. This is done to remove the dew from the ball so that they can grip the ball better.
And when the ball gets older say 30 overs then bowlers shine one side to get reverse swing.
Explanation:
Rather it's the other way round. Cricket bowlers rub the ball on their trousers or jerseys by applying sweat or saliva for maintaining the shine, so that it does not go away and facilitates swing bowling. Just as in case for leather shoes, where the cobbler shines by rubbing it with a brush or cloth, so also a bowler rubs the leather ball in order to maintain the shine.
Coming to your second question, if balls were manufactured in such a way, so that it came with one side polished and the other side rough, then it would have reverse swung from beginning. With only one side being as good as a normal new ball (both side polished), the ball you are talking about(one side roughened up) would have deteriorated much faster and would have made it a no match for fast bowlers.
Hope this answers your question