The masses of two substances are $4 \text{ g}$ and $9 \text{ g}$ respectively. If their kinetic energies are the same,then the ratio of their momenta will be

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

$A$ man who is running has half the kinetic energy of a boy of half his mass. The man speeds up by $1 \,ms^{-1}$ and then has the same kinetic energy as the boy. The initial speed of the boy is

The work done by a force on a body of mass $5 \,kg$ to accelerate it in the direction of the force from rest to $20 \,m/s$ in $10 \,s$ is:

The kinetic energy of a body moving along a straight line varies with time as shown in the figure. The force acting on the body is:

If the kinetic energy of a body increases by $0.1\%$,the percent increase of its momentum will be .............. $\%$