The frictional force opposes the forward motion of the crate. The coefficient of static friction is 0.2.
Using the formula;
Fa = - Ff + mgsinθ
but Ff = μsFN and N = mgcosθ
Hence;
Fa = mgsinθ - μsmgcosθ
μsmgcosθ = mgsinθ - Fa
μk = mgsinθ - Fa/mgcosθ
μk = coefficient of static friction = ?
Fa = horizontal force = 100N
m = mass = 30.6 kg
θ = angle = 30°
g = acceleration due to gravity = 10 m/s^2
Substituting values;
μk = [(30.6 × 10) sin 30°] - 100 / (30.6 kg × 10) cos 30°
μk = 153 - 100/265
μk = 0.2
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