Question

Two blocks of masses $m_{1}$ and $m_{2}$ are connected through a massless inextensible string. Block of mass $m_{1}$ is placed at the fixed rigid inclined surface while the block of mass $m_{2}$ hanging at the other end of the string, which is passing through a fixed massless frictionless pulley shown in figure-$2.193$. The coefficient of static friction between the block and the inclined plane is $0.8$. The system of masses $m_{1}$ and $m_{2}$ is released from rest. (Take $g=10\, m / s ^{2}$ )

• A. the tension in the string is $20\, N$ after releasing the system
• B. the contact force by the inclined surface on the block is along normal to the inclined surface
• C. the magnitude of contact force by the inclined surface on the block $m_{1}$ is $20 \sqrt{3} N$
• D. none of these

Answer 1

Answer: (A), (B), (C)

As $m_{1} g \sin 30^{\circ}=m_{2} g=T$, no friction will act on $m_{1}$ so $T=20\, N$ and net contact force on $m_{1}$ is the normal reaction by ground which is $m_{1} g \cos 30^{\circ}=20 \sqrt{3} N$