Physics - NLM Question with Solution | TestHub

When we walk, our feet are pushing ground backwards and therefore the friction opposes the pushing and acts in the opposite direction which happens to be the direction in which we are walking.

Hence we can say friction works in the direction of walking

Normal reaction $N=Mg$ ( as per free body diagram )

Maximum acceleration $a_{max}=\frac{f_{max}}{M}=\frac{\mu Mg}{M}=\mu g$