A body of mass $10\,kg$ at rest is acted upon simultaneously by two forces $4 \,N$ and $3\,N$ at right angles to each other. The kinetic energy of the body at the end of $10 \,sec$ is .............. $\mathrm{J}$

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 )$

Two masses of $1 \,gm$ and $4 \,gm$ are moving with equal kinetic energies. The ratio of the magnitudes of their linear momenta is

A particle is dropped from a height $h$. A constant horizontal velocity is given to the particle. Taking $g$ to be constant every where, kinetic energy $E$ of the particle w. r. t. time t is correctly shown in

The mass of two substances are $4gm$ and $9gm$ respectively. If their kinetic energies are same, then the ratio of their momenta will be

The same retarding force is applied to stop a train. The train stops after $80 m$. If the speed is doubled, then the distance will be