A particle of mass $m$ collides with a heavy mass (at rest) elastically and after collision returns with $4/9$ of it's initial kinetic energy. The mass of heavy object is ............... $\mathrm{m}$
$5$
$3$
$7$
$2$
A sphere of mass $m $ moving with a constant velocity $u$ hits another stationary sphere of the same mass. If $e$ is the coefficient of restitution, then the ratio of the velocity of two spheres after collision will be
A moving block having mass $m,$ collides with another stationary block having mass $4\,m$ . The lighter block comes to rest after collision. When the initial velocity of the lighter block is $v,$ then the value of coefficient of restitution $( e)$ will be
A moving particle of mass $m,$ makes a head on elastic collision with another particle of mass $2\,m,$ which is initially at rest. The percentage loss in energy of the colliding particle on collision, is close to .................. $\%$
A bullet of mass $m$ strikes a block of mass $M$ connected to a light spring of stiffness $k$ , with a speed $V_0$ . If the bullet gets embedded in the block then, the maximum compression in the spring is
A proton of mass $m$ collides elastically with a particle of unknown mass at rest. After the collision, the proton and the unknown particle are seen moving at an angle of $90^o$ with respect to each other. The mass of unknown particle is