# A block rests on a rough inclined plane making an angle of $30 ^{\circ}$ with the horizontal. The coefficient of static friction between block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of block is $(g=10 m/s^2)$

$(a)\;2.0\;kg \quad (b)\;4.0\; kg \quad (c)\;1.6\; kg \quad (d)\;2.5\; kg$

$F=mg \times \sin \theta$
$10= m \times 10 \times \sin 30 ^{\circ}$
$m=2 \;kg$
Hence a is the correct answer.

edited Feb 10, 2014 by meena.p