$A$ river of salty water is flowing with a velocity $2 ~m/s$. If the density of the water is $1.2 ~g/cc$,then the kinetic energy of each cubic metre of water is

Choose the correct statement$(s)$:
$(A)$ The position of the centre of mass of a system is dependent on the choice of the coordinate system.
$(B)$ Newton's second law of motion is applicable to the centre of mass of the system.
$(C)$ Internal forces cannot change the state of the centre of mass.
$(D)$ Internal forces can change the state of the centre of mass.

Two capacitors $C_1$ and $C_2$ in a circuit are joined as shown below. The potential of point $A$ is $V_1$ and that of $B$ is $V_2$. The potential of point $D$ will be

The wavelength of a $1 \ keV$ photon is $1.24 \times 10^{-9} \ m$. What is the frequency of a $1 \ MeV$ photon?

In Young's double slit experiment,the phase difference between the light waves reaching the third bright fringe from the central fringe is $(\lambda = 6000 \ \mathring{A})$

The sum of the magnitudes of two forces acting at a point is $16 ~N$. If their resultant is normal to the smaller force and has a magnitude of $8 ~N$,then the forces are: