The upper half of an inclined plane with inclination $\phi$ is perfectly smooth, while the lower half is rough. $A$ body starting from rest at the top will again come to rest at the bottom, if the coefficient of friction for the lower half is given by-
$2 \sin \phi$
$2 \cos \phi$
$2 \tan \phi$
$ \tan \phi$
A block of mass $M$ has a circular cut with a frictionless surface as shown. The block rests on the horizontal frictionless surface of a fixed table. Initially the right edge of the block is at $x=0$, in a co-ordinate system fixed to the table. A point mass $m$ is released from rest at the topmost point of the path as shown and it slides down. When the mass loses contact with the block, its position is $\mathrm{x}$ and the velocity is $\mathrm{v}$. At that instant, which of the following options is/are correct?
(image)
$[A]$ The $x$ component of displacement of the center of mass of the block $M$ is : $-\frac{m R}{M+m}$.
[$B$] The position of the point mass is : $x=-\sqrt{2} \frac{\mathrm{mR}}{\mathrm{M}+\mathrm{m}}$.
[$C$] The velocity of the point mass $m$ is : $v=\sqrt{\frac{2 g R}{1+\frac{m}{M}}}$.
[$D$] The velocity of the block $M$ is: $V=-\frac{m}{M} \sqrt{2 g R}$.
A projectile of mass $M$ is fired so that the horizontal range is $4\, km$. At the highest point the projectile explodes in two parts of masses $M/4$ and $3M/4$ respectively and the heavier part starts falling down vertically with zero initial speed. The horizontal range (distance from point of firing) of the lighter part is .................. $\mathrm{km}$
$A$ block of mass $m$ starts from rest and slides down $a$ frictionless semi-circular track from $a$ height $h$ as shown. When it reaches the lowest point of the track, it collides with a stationary piece of putty also having mass $m$. If the block and the putty stick together and continue to slide, the maximum height that the block-putty system could reach is:
As per the given figure, two blocks each of mass $250\,g$ are connected to a spring of spring constant $2\,Nm ^{-1}$. If both are given velocity $V$ in opposite directions, then maximum elongation of the spring is: