A stone tied to a string of length $L$ is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position and has a speed $u$. The magnitude of the change in its velocity as it reaches a position where the string is horizontal is

A bob of mass m suspended by a light string of length $L$ is whirled into a vertical circle as shown in figure. What will be the trajectory of the particle, if the string is cut at $(a)$ point $B$ ? $(b)$ point $C$ ? $(c) $ point $X$ ?

$A$ particle of mass $m$ is released from $a$ height $H$ on $a$ smooth curved surface which ends into a vertical loop of radius $R$, as shown If $\theta$ is instantaneous angle which the line joining the particle and the centre of the loop makes with the vertical, then identify the correct statement $(s)$ related to the normal reaction $N$ between the block and the surface

A stone of mass $m$ is tied to a string and is moved in a vertical circle of radius $r$ making $n$ revolutions per minute. The total tension in the string when the stone is at its lowest point is 

A block follows the path as shown in the figure from height $h$. If radius of circular path is $r$, then relation that holds good to complete full circle is