MCQ
Consider the diagram shown below in which two masses of $m$ and $2 m$ are placed on a fixed triangular wedge. The coefficient of friction between block $A$ and the wedge is $2 / 3$, while that for block $B$ and the wedge is $1 / 3$
  • $zero$
  • B
    $\frac{2 m ^2}{3}\,g$
  • C
    $\frac{4 m ^2}{3}\,g$
  • D
    $\frac{ m ^2}{\sqrt{2}} g$

Answer

Correct option: A.
$zero$
a
(a)

Given,

$\mu_2=\frac{2}{3} \text { and } \mu_0=\frac{1}{3}$

Let the acceleration of the whole system be a then,

As per the diagram,

For block $B$,

$2 mg \cos 45^{\circ}+2 ma = T +\mu_0 N _{ b }$

$N _{ b }=2 mg \sin 45^{\circ}$

And, For block $A$,

$T =m g \cos 45^{\circ}+\mu_g N_a$

$N_{ a }=m g \sin 45^{\circ}$

So,

$T=m g \cos 45^{\circ}+\mu_2 m g \sin 45^{\circ} \ldots \ldots$

From eq $(1)$ and $(2)$

$2 m g \cos 45^{\circ}+2 ma =m g \cos 45^{\circ}+\mu_2 m g \sin 45^{\circ}+\mu_0 2 m g \sin 45^{\circ}$

After solving, We get $a =0$

So the acceleration of the block $A$ will be zero.

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