Laws Of Motion Question 391

Question: A weight w is to be moved from the bottom to the top of an inclined plane of inclination 9 to the horizontal. If a smaller force is to be applied to drag it along the plane in comparison to lift it vertically up, the coefficient of friction should be such that:

Options:

A) $ \mu >\tan ( \frac{\pi }{4}-\frac{\theta }{2} ) $

B) $ \mu <\tan ( \frac{\pi }{4}-\frac{\theta }{2} ) $

C) $ \mu <\tan \theta $

D) $ \mu >\tan \frac{\pi }{4} $

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Answer:

Correct Answer: B

Solution:

$ F _{1}=w\sin \theta +\mu w\cos \theta $

$ F _{2}=w $

As,$ F _{1}<F _{2} $

$ \therefore \mu <\tan ( \frac{\pi }{4}=\frac{\theta }{2} ) $



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