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Determine the force P to cause the motion to impend. Take masses of the block A & B as 8 kg & 4 kg respectively and the coefficient of sliding friction as 0.3. The force P and the rope are parallel to the inclined plane. Assume frictionless pulley.[F…

Q.5 (A) Determine the force P to cause the motion to impend. Take masses of the block A & B as 8 kg & 4 kg respectively and the coefficient of sliding friction as 0.3. The force P and the rope are parallel to the inclined plane. Assume frictionless pulley.

[Figure: an incline rising to the right at 30° to the horizontal. A frictionless pulley is fixed at the upper end of the incline. Block A (lower on the incline) and block B (higher up) both rest on the incline. A rope from the upper side of A runs up parallel to the incline, over the pulley, and comes back down parallel to the incline to block B. Force P pulls A down the incline, parallel to it.]

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Given: \(m_A = 8\) kg (\(W_A = 78.48\) N), \(m_B = 4\) kg (\(W_B = 39.24\) N), \(\mu = 0.3\), \(\theta = 30^\circ\). When P pulls A down the plane, the rope pulls B up the plane. Friction opposes each motion.

Block B (impending motion up the plane): \(N_B = 39.24\cos30^\circ = 33.98\) N, \(F_B = 0.3 \times 33.98 = 10.19\) N (down the plane)

\(T = W_B\sin30^\circ + F_B = 19.62 + 10.19 = 29.81\) N

Block A (impending motion down the plane): \(N_A = 78.48\cos30^\circ = 67.97\) N, \(F_A = 0.3 \times 67.97 = 20.39\) N (up the plane)

Along the plane: \(P + W_A\sin30^\circ = T + F_A \Rightarrow P + 39.24 = 29.81 + 20.39\)

Answer: P = 10.96 N (down the plane).

Doubtly AI · 25 Oct 2026 AI-verified · Oct 2026 Report
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