$A$ person used force $(F)$,shown in the figure,to move a load with a constant velocity on a given surface. Identify the correct surface profile.

$A$ point particle of mass $m$ moves along the uniformly rough track $PQR$ as shown in the figure. The coefficient of friction between the particle and the rough track equals $\mu$. The particle is released from rest from the point $P$ and it comes to rest at a point $R$. The energies lost by the particle over the parts $PQ$ and $QR$ of the track are equal to each other,and no energy is lost when the particle changes direction from $PQ$ to $QR$. The values of the coefficient of friction $\mu$ and the distance $x (= QR)$ are,respectively,close to

Block $B$ of mass $100 \ kg$ rests on a rough surface with a friction coefficient $\mu = 1/3$. $A$ rope is tied to block $B$ as shown in the figure. The maximum acceleration with which boy $A$ of mass $25 \ kg$ can climb the rope without making the block move is:

If the overbridge is concave instead of being convex,the thrust on the road at the lowest position will be

$A$ rough inclined plane $BCE$ of height $\left(\frac{25}{6}\right) \text{ m}$ is kept on a rectangular wooden block $ABCD$ of height $10 \text{ m}$,as shown in the figure. $A$ small block is allowed to slide down from the top $E$ of the inclined plane. The coefficient of kinetic friction between the block and the inclined plane is $\frac{1}{8}$ and the angle of inclination of the inclined plane is $\sin^{-1}(0.6)$. If the small block finally reaches the ground at a point $F$,then $DF$ will be (Acceleration due to gravity,$g=10 \text{ ms}^{-2}$)

$A$ particle initially at rest is subjected to two forces. One is constant,the other is a retarding force proportional to the particle velocity. In the subsequent motion of the particle,