Question

Blocks A and B in the figure are connected by a bar of negligible weight. If A = B = 170 kg &m_A = 0.2 and m_B = 0.4, where m_A and m_B are the coefficients of limiting friction between blocks and plane, calculate the force on the bar : (g = 10 m/s²)

• A. 150 N
• B. 75 N
• C. 200 N
• D. 250 N

Answer 1

Answer: (A)

150 N

Answer 2

For (1) ® mgsinq – T –m_Amgcosq = ma .…(1)

For (2) ® T + mgsinq –m_Bmgcosq = ma ....(2)

̃ mgsinq –T–m_Amgcosq = T + mgsinq –m_Bmgcosq

̃ T = $\frac { m g \cos \theta } { 2 }$ (m_B–m_A)

= $\frac { 170 \times 10 \times 15 / 17 } { 2 }$ (0.4–0.2) = 150N