A force of 98N is just able to move a block 20 kg (but the block is on the rest ) on a rough surface. Calculate the coefficient of friction.
Given: F = 98N
The block is on rest then f s = F = 98N
μ s = f s / R = f s / mg
μ s = 98N/ 20kg* 9.8ms^-2 = 0.5