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 .......... $mg$.

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:

$A$ smooth right-angled wedge of mass $M$ is kept on a smooth horizontal surface as shown. $A$ mass $m$ is released from the top of the wedge. When $m$ reaches the ground, its speed is $V$. Find the work done by the normal contact force on $m$ while it comes down to the ground.

$A$ freely falling body has attained a velocity of $2 \,m/s$. If the weight of the body is now opposed by a constant upward air resistance force equal to its weight, what is the total distance travelled by the body before it comes to rest (in $\,m$)?

An elevator of mass $500 \,kg$ is ascending upwards with a constant acceleration $a=2 \,m/s^2$. What is the work done by the tension in the elevator cable during its climb by $12 \,m$ (in $\,kJ$)? (Take $g=10 \,m/s^2$)

If the breaking strength of a rope is $\frac{4}{3}$ times the weight of a person,then the maximum acceleration with which the person can safely climb up the rope is ($g$ = acceleration due to gravity).