Question

A block of mass $mkg$ is sliding from rest on an inclined rough surface of inclination ) as shown in the figure under the action of three forces, weight, normal and frictional force only The magnitude of forces are $20N,40Nand50N$ not necessarily in the same order The value of $g$ is 10 $m/s^2$ Now match the physical quantity in List I with their magnitude in List II in SI unit and select the correct answer .

Answer 1

Weight of block$=mg$

Normal acting on the block$=\mu mg$

Frictional force acting on block$=\mu N=\mu mgcos\theta$

$⟹mg>mgcos\theta >\mu mgcos\theta$

Since $50N>40N>20N$,

$mg=50N$

$mgcos\theta =40N$

$\mu mgcos\theta =20N$

$⟹cos\theta =\frac{4}{5}$,

& $\mu =0.5$

A) $mg=50N$

$⟹m=5kg$

B) $a=gsin\theta -\frac{f}{m}=6-\frac{20}{5}=2m/s^2$

C) Net force acting on block during motion$=ma=10N$

D)$\mu =0.5$

$⟹8\mu =4$