Answers

2014-10-08T19:18:56+05:30
Due to the frictional force we can walk ,write,hold the objects etc so frictional force is a friend  wear and tear of machine parts,slipping on a smooth road are also due to frictional force .so it can be considered as evil 
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2014-10-08T20:39:15+05:30
Friction is advantageous in the following ways:
1.walking in the floor
2.nails are held in the wall
3.helps fingers to hold a pen
4.vehicles move on the road
5.mechanical power transmission of belt-drive
disadvantages of friction:
1.large amount of power loss in engines
2.wear and tear of machines increases reducing their life
3.causes unnecessary heating if machine parts thereby causing malfunctioning
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