Question

Two blocks are connected over a massless pulley as shown in figure. The mass of block A is 10 kg and the coefficient of kinetic friction is 0.2. Block A slides down the incline at constant speed. The mass of block B in kg is

• A. 5.4
• B. 3.3
• C. 4.2
• D. 6.8

Answer 1

The correct option is B 3.3

Net pulling force on the system should be zero, as velocity is constant. Hence,
$m_{A}gsin{30}^{\circ }=\mu m_{A}gcos{30}^{\circ }+m_{B}g$
$\therefore m_B=\left(\frac{m_A}{2}\right)-\left(\frac{\mu m_A\sqrt{3}}{2}\right)$
$=10[\frac{1}{2}-0.2\times \frac{\sqrt{3}}{2}]=3.3kg$