After head on elastic collision between two balls of equal masses , one is observed to have a speed of $3\,\,m/s$ along positive $x-$ axis and the other has a speed of $2\,\,m/s$ along negative $x$ axis. The original velocities of the balls are
$-2\,\,m/s\,\,$ and $\,\,+3\,\,m/s$
$+2\,\,m/s\,\,$ and $\,\,+3\,\,m/s$
$-3\,\,m/s\,\,$ and $\,\,+2\,\,m/s$
$+3\,\,m/s\,\,$ and $\,\,-2\,\,m/s$
A ball after falling from a height of $10\, m$ strikes the roof of a lift which is descending down with a velocity of $1\, m/s$. The recoil velocity of the ball will be .............. $\mathrm{m}/ \mathrm{s}$
A body of mass $m$ is accelerated uniformly from rest to a speed $v$ in a time $T$. The instantaneous power delivered to the body as a function of time is given by
A uniform flexible chain of mass $m$ and length $2l$ hangs in equilibrium over a smooth horizontal pin of negligible diameter. One end of the chain is given a small vertical displacement so that the chain slips over the pin. The speed of chain when it leaves pin is
A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement $x$ is proportional to
The work done by a force $\vec F = \left( { - 6{x^3}\hat i} \right)\,N$ in displacing a particle from $x = 4\,m$ to $x = -2\,m$ is ............... $\mathrm{J}$