# Four blocks placed in contact on an inclined plane as shown in the figure. The coefficients of friction ….

Q: Four blocks placed in contact on an inclined plane as shown in the figure. The coefficients of friction between inclined plane and these blocks are μ1 , μ2 , μ3 and μ4 respectively with μ1 > μ2 > μ3 > μ4. The minimum value of tanα at which the blocks start sliding down is

(a) $\frac{m_1 m_2 + m_2 m_3 + m_3 m_4}{(\mu_1 m_1 + \mu_2 m_2 + \mu_3 m_3 + \mu_4 m_4) (m_1 +m_2 + m_3 + m_4)}$

(b) $\frac{\mu_1 m_1 + \mu_2 m_2 + \mu_3 m_3 + \mu_4 m_4}{m_1 +m_2 + m_3 + m_4}$

(c) $\mu_1 + \mu_2 + \mu_3 + \mu_4$

(d) $\frac{m_1 +m_2 + m_3 + m_4}{\mu_1 m_1 + \mu_2 m_2 + \mu_3 m_3 + \mu_4 m_4}$

Ans: (b)