1.

A block slides from an inclined plane of inclination 45^(@)If it takes twice the time with friction than that without friction, the coefficient of friction between block and surface is :

Answer»

1
`0.75`
`0.5`
`0.25`

Solution :Acc. without friction `a_(1) = g sin THETA`
Acc. with friction `a_(2) = g sin theta- mug COS theta`
Now `(t_(1))/(t_(2))=sqrt(a_(2)/(a_(1))) or(t_(2))/(t_(1))=sqrt(a_(1)/(a_(2)))`
`2=sqrt((gsintheta)/(gsin theta- mug cos theta))`
`4=(sin theta)/(sin theta-mu cos theta)=(1)/(1-mu tan theta)`
`4=(1)/(1-mu)=1 or(As theta=45^(@)`
`4-4mu=1 or 4mu=3mu=3//4=0.75`
(b) is the choice.


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