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Problem 3 - Entrance Test

A block of mass 2 kg is placed on a rough inclined plane with an angle of inclination of 30°. The coefficient of static friction between the block and the plane is 0.5. What is the minimum force required to keep the block from sliding down the plane? (g = 10 m/s²)

Correct: A

The force required is F = mg(sinθ - μcosθ) = 2 * 10 * (sin30° - 0.5 * cos30°) = 20 * (0.5 - 0.5 * √3/2) = 20 * (0.5 - 0.5 * 0.866) = 20 * (0.5 - 0.433) = 20 * 0.067 = 1.34 N. Since the value is > 0. the block will slide without applying force. Thus F=0.