Can friction do positive work? If yes explain with an example? If friction can do positive work, then (from work-energy theorem) friction can increase the kinetic energy of an isolated system. Give your views on this statement.
39yes friction force can do positive work as we can see in many rotaational motion problems..
we can even see that frcition does positive or negative work depending on the frame of reference from which we are looking at it
39example:
think of a small block resting on top of a larger block.
If the bottom block accelerates it will drag the top block with it.
Since the force of friction on the small block and it's displacement are in the same direction, the work done by friction is positive.
62even in linear motion... I would say a lot more times than it does negative work!
even in real world, if i have to say, i would say that friction does +ve work with probably as much frequency as it does -ve work!
No one thinking yet!
1ans part (ii):- In case of an isolated system, friction can never do a positive work.
taking the example of the two block system, we see that friction does a positive work for the
upper block but simultaneously it does a negative work on the lower block, equal in magnitude, thus the net work done on this isolated system of two blocks is zero.
If it were possible to generate positive work ( or kinetic energy ) from friction , then lot of
problems in the world would have been solved.
23I havent understood one thing on this post ....
experts themselves asked the question .... and experts them selves answered it !!!!
isnt that a bit strange ??? [7]
23by the way pankaj sir this question was very well discussed even earlier .......u may hav a look at it
http://targetiit.com/iit-jee-forum/posts/silly-doubts-12498.html
