Two masses $A$ and $B$ of $10\, kg$ and $5 \,kg$ respectively are connected with a string passing over a frictionless pulley fixed at the corner of a table as shown. The coefficient of static friction of $A$ with table is $0.2$. The minimum mass of $C$ that may be placed on $A$ to prevent it from moving is ........ $kg$
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(a) For limiting condition $\mu = \frac{{{m_B}}}{{{m_A} + {m_C}}}$ $⇒$ $0.2 = \frac{5}{{10 + {m_C}}}$
$⇒$ $2 + 0.2{m_C} = 5$ $⇒$ ${m_C} = 15\,kg$
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