A man (mass $= 50\, kg$) and his son (mass $= 20\, kg$) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of $0.70\, ms^{-1}$ with respect to the man. The speed of the man with respect to the surface is ........ $ms^{-1}$

The momentum of a system is conserved

An object of mass $3\,m$ splits into three equal fragments. Two fragments have velocities $v\hat j$ and $v\hat i$. The velocity of the third fragment is

A shell of mass $m$ moving with velocity $ v$ suddenly breaks into $2$ pieces. The part having mass $m/4$ remains stationary. The velocity of the other shell will be

A vessel at rest explodes into three pieces. Two pieces having equal masses fly off perpendicular to one another with the same velocity $30$ meter per second. The third piece has three times mass of each of other piece. The magnitude and direction of the velocity of the third piece will be

A man is standing at the centre of frictionless pond of ice. How can he get himself to the shore