A block rests on a horizontal surface where and

PHYSICS · Single correct · CBSE · Physics · Laws of Motion · Laws of Motion

Problem

A 4.0 kg4.0\,\text{kg} block rests on a horizontal surface where μs=0.40\mu_s = 0.40 and μk=0.30\mu_k = 0.30. Three horizontal forces act simultaneously on the block: a 18 N18\,\text{N} push to the right, a 12 N12\,\text{N} pull to the left, and a 9 N9\,\text{N} wind force to the right. Which of the following best describes what happens immediately after the forces are applied? (a) The block accelerates to the right at 2.3 m/s22.3\,\text{m/s}^2 because static friction is limited to only 6 N6\,\text N. (b) The block accelerates slightly to the left at 0.17 m/s20.17\,\text{m/s}^2 because the maximum static friction exceeds the applied forces. (c) The block remains at rest because static friction can supply the necessary 15 N15\,\text{N} opposing force. (d) The block accelerates to the right at 0.81 m/s20.81\,\text{m/s}^2 because kinetic friction acts after the block begins to slide.

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