JEE MAIN - Physics (2004 - No. 74)
A block rests on a rough inclined plane `making an angle of $${30^ \circ }$$ with the horizontal. The coefficient of static friction between the block and the plane is $$0.8.$$ If the frictionless force on the block is $$10$$ $$N,$$ the mass of the block (in $$kg$$) is $$\left( {take\,\,\,g\, = \,10\,\,m/{s^2}} \right)$$
$$1.6$$
$$4.0$$
$$2.0$$
$$2.5$$
Explanation
For equilibrum of block,
$$mg\,\,\sin \theta = {f_s}\,\,$$
$$ \Rightarrow m \times 10 \times \sin {30^ \circ } = 10$$
$$ \Rightarrow m \times 5 = 10$$
$$ \Rightarrow m = 2.0\,\,kg$$
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