Question

A block $A$ with mass $100kg$ is resting on another block $B$ of mass $200kg$. As shown in figure a horizontal rope tied to a wall holds it. The coefficient of friction between $A$ and $B$ is $0.2$ while coefficient of friction between $B$ and the ground is $0.3$ . The minimum required force $F$ (in$N$) to start moving $B$ will be:

Answer 1

$F=f_{AB}+f_{BG}$
$={\mu }_{AB}{m}_{A}g+{\mu }_{BG}(m_A+m_B)g$
$=0.2\times 100\times 10+0.3\left(300\right)\times 10$
$=200+900=1100N$

Final Answer: 1100 N