Question

A boy of mass $M$ is applying a horizontal force to slide a box of mass $M_1$ on a rough horizontal surface. The coefficient of friction between the shoe of the boy and the floor is $\mu$ and that between the box and the floor is ${\mu }_1$. In which of the following cases it is certainly not possible to slide the box?

• A. $\mu <{\mu }_1:M<M_1$
• B. $\mu >{\mu }_1:M>M_1$
• C. $\mu <{\mu }_1:M>M_1$
• D. $\mu >{\mu }_1:M<M_1$

Answer 1

The correct option is A $\mu <{\mu }_1:M<M_1$

If $\mu <{\mu }_1$ and $M<M_1$, in this case the friction force between and ground is less then that of box. Boy will slip before box moves as friction between boy and ground is less than that between box and ground.