Question

Starting from rest , a body slides down at `45^(@)` inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is
A. `0.33`
B. `0.25`
C. `0.75`
D. `0.80`

Answer 1

Correct Answer - C
Smooth surface : `a_(1) = g sin 45^(@) , t_(1) = t`
Rough surface : `a_(2) = g sin 45^(@) 0 mu g cos 45^(@) , t_(2) = 2t`
`s = (1)/(2) a_(1) t_(1)^(2) = (1)/(2) a_(2) t_(2)^(2)`
`( g sin 45^(@)) t^(2) = ( g sin 45^(@) - mu g cos 45^(@)) ( 2t)^(2)`
`1 = ( 1 - mu) 4 rArr mu = (3)/(4) = 0.75`