A bomb of mass $16\ kg$ at rest explodes into two pieces of masses $4\ kg$ and $12\ kg.$ The velolcity of the $12\ kg$ mass is $4$ $ms^{-1}$. The kinetic energy of the other mass is ………….. $\mathrm{J}$

A bullet of mass $50 \mathrm{~g}$ is fired with a speed $100 \mathrm{~m} / \mathrm{s}$ on a plywood and emerges with $40 \mathrm{~m} / \mathrm{s}$. The percentage loss of kinetic energy is :

An electron and a proton are detected in a cosmic ray experiment, the first with kinetic energy $10\; keV$, and the second with $100\; keV$. Which is faster, the electron or the proton? Obtain the ratio of their speeds. (electron mass $=9.11 \times 10^{31}\; kg$. proton mass $=1.67 \times 10^{-27}\;$$ kg , 1 \;eV =1.60 \times 10^{-19} \;J )$

A car travelling at a speed of $30\, km/hour$  is brought to a halt in $8\, m$ by applying brakes. If the same car is travelling at $60 \,km/hour$, it can be brought to a halt with the same braking force in …………… $\mathrm{m}$

If the coefficient of restitution be $0.5,$ what is the percentage loss of energy on each rebounding of a ball dropped from a height ………… $\%$