As shown in the figure, pulley a weighs 40n, pulley B and pulley C each weighs 20n, and weight g = 200N. Solution: regardless of the influence of stay wire mass and pulley rotation friction, the free end of the rope can just move downward at 60mm / s under the action of force F, what is the force F? How much distance can weight g rise in one minute? (the rope is long enough)

(1) There are three sections of rope pulling the pulley, so f = 13 (g moving + G object) = 13 × (40n + 200N) = 80N (2) the rope end rises in 1min, s = V rope · t = 0.06m/s × 60s = 3.6m. Because there are three sections of rope pulling the heavy object, the object rising distance h = 13s = 13 × 3.6m = 1.2m A: the pulling force F is 80N; the heavy object rises 1.2m

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