You want to apply a force on a box so that it moves with constant speed across a horizontal floor. The coefficient of kinetic friction between the box and the floor is ${\mathrm{\mu }}_{\mathrm{k}}$. Of the four following cases, the force you apply on the box will be smallest when you

Assertion: A horse has to pull a cart harder during the first few steps of his motion.

Reason: The first few steps are always difficult.

Consider a liquid at rest in a container which opens into the atmosphere. At any point $A$ at a depth $h$ below the surface of the liquid,

(i) the gauge pressure at point $A$ is $\rho gh$.

(ii) the gauge pressure at point $A$ is $P_{\mathrm{a}}+\rho gh$.

(iii) The pressure at point $A$ is $\rho gh$.

(iv) The pressure at point $A$ is $P_{\mathrm{a}}+\rho gh$.

The correct alternative is