A 3-kg block of wood is on a level surface where μs=0.25 and μk=0.2. A force of 7 N is being applied horizontally to the block. Mark the correct statement(s) regarding this situation.

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If the block is initially at rest, it will remain at rest and friction force will be about 7 N.

If the block is initially moving, then it will continue its motion forever if the force applied is in the direction of the motion of the block.

If the block is initially moving and the direction of applied force is same as that of motion of block, then block moves with an acceleration of 1/3ms−2along its initial direction of motion.

If the block is initially moving and direction of applied force is opposite to that of initial motion of the block, then the block decelerates, comes to a stop, and starts moving in the opposite direction.

answer is A.

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Detailed Solution

If the block is at rest, then force applied has to be greater than limiting friction force for its motion to begin.fL=μsmg=0.25×3g=7.5Nfk the block is accelerated with an acceleration of a=F−fkm=13ms−2 and hence its speed is continuously increasing.If applied force is opposite to direction of motion, then block is under deceleration of a=−F+fkm=−133ms−2 and hence after some time block stops and kinetic friction vanishes but applied force continues to act.But as F

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