Coefficient of friction: μ = F/N
μ =15 N
F =35 N
N = ?
N = μ / F
= 15 / 35
= 0.42
"Coefficient of friction, ratio of the frictional force resisting the motion of two surfaces in contact to the normal force pressing the two surfaces together. It is usually symbolized by the Greek letter mu (μ). Mathematically, μ = F/N, where F is the frictional force and N is the normal force."
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