$A$ plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches $30^o$,the box starts to slip and slides $4.0\, m$ down the plank in $4.0\, s$. The coefficients of static and kinetic friction between the box and the plank will be,respectively:

$A$ block of mass $M$ is placed on a horizontal surface and is tied with an inextensible string to a block of mass $m$,as shown in the figure. $A$ block of mass $m_0$ is also placed on $M$. The surface under $M$ is smooth,while the vertical surface under $m$ is rough with a coefficient of friction $\mu$. The minimum value of $\mu$ for which the block $m$ remains stationary is:

In the figure shown,all surfaces are frictionless,and the mass of the block is $m = 1\, kg$. The block and wedge are held initially at rest. Now,the wedge is given a horizontal acceleration of $a = 10\, m/s^2$ by applying a force on the wedge,such that the block does not slip on the wedge. Calculate the work done by the normal force in the ground frame on the block in $\sqrt{3}$ seconds. (Assume $\tan \theta = a/g = 1$,so $\theta = 45^\circ$)

When forces $F_1, F_2, F_3$ are acting on a particle of mass $m$ such that $F_2$ and $F_3$ are mutually perpendicular,the particle remains stationary. If the force $F_1$ is now removed,the acceleration of the particle is:

$A$ man can move on a horizontal plank supported symmetrically as shown. The variation of normal reaction on support $A$ with distance $x$ of the man from the end of the plank is best represented by:

Two observers are moving at a constant velocity $v$ relative to each other along a straight line. They observe a block of mass $m$ moving over a distance $l$ on a rough surface. Which of the following quantities will be the same for both observers?