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4-1.Newton's Laws of Motion
normal
A block of mass $m$ lying on a rough horizontal plane is acted upon by a horizontal force $P$ and another force $Q$ inclined an at an angle $\theta$ to the vertical. The minimum value of coefficient of friction between the block and the surface for which the block will remain in equilibrium is :
A
$\frac{P \cos \theta+Q}{m g-Q \sin \theta}$
B
$\frac{P+Q \sin \theta}{m g+Q \cos \theta}$
C
$\frac{P+Q \cos \theta}{m g+Q \sin \theta}$
D
$\frac{P \sin \theta-Q}{m g-Q \cos \theta}$
Solution
$f_r=\mu N=\mu(m g+Q \cos \theta)$
$f_r=P+Q \sin \theta$
$\mu=\frac{(P+Q \sin \theta)}{(m g+Q \cos \theta)}$
Standard 11
Physics
