A 5 kg block lies on a rough horizontal floor with coefficient of static friction 0.4. Two horizontal forces 30 N towards right and 15 N towards left act simultaneously. Take g = 10 m/s². The magnitude of friction force is:
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Question

A 5 kg block lies on a rough horizontal floor with coefficient of static friction 0.4. Two horizontal forces 30 N towards right and 15 N towards left act simultaneously. Take g = 10 m/s². The magnitude of friction force is:

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G1 Physics · Accepted Answer

Without friction the net applied force is 15 N towards right. Maximum static friction is μₛmg = 0.4×5×10 = 20 N. Since 15 N < 20 N, the block remains at rest and static friction is 15 N towards left. Magnitude = 15 N.