Ten one-rupee coins are placed on top of each other on a table. Each coin has mass $m$. The reaction force of the $6^{th}$ coin (counted from the bottom) on the $7^{th}$ coin is .......... $mg$.

The figure shows a boy on a horizontal platform $A$ on a smooth horizontal surface,holding a rope attached to a box $B$. The boy pulls the rope with a constant force of $50 \ N$. (The boy does not slip over the platform). The combined mass of platform $A$ and the boy is $250 \ kg$,and that of box $B$ is $500 \ kg$. The velocity of $A$ relative to the box $B$,$5 \ s$ after the boy on $A$ begins to pull the rope,will be ............ $m/s$.

Three identical particles of mass $m$ are joined together by a thread as shown in the figure. All three particles are moving in a horizontal plane in a circle about the point $O$. If the velocity of the outermost particle is $v_0$,then the ratio of tensions in the three sections of the string is:

Three blocks $A, B$ and $C$ weighing $1 \, kg, 8 \, kg$ and $27 \, kg$ respectively are connected as shown in the figure with an inextensible string and are moving on a smooth surface. If ${T_3} = 36 \, N$,then find the value of ${T_2}$ in $N$.

$A$ 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 $M$. If the surface between $M$ and $m_0$ has a coefficient of friction $\mu$,find the tension in the string,assuming the system moves together.

$A$ dynamometer $D$ is attached to two blocks of masses $6 \, kg$ and $4 \, kg$ as shown in the figure. The reading of the dynamometer is ............ $N$.