$A$ man pushes a wall and fails to displace it. He does:

Consider the following statements $A$ and $B$. Identify the correct choice in the given answer.
$A$. $p-n, p-p$ and $n-n$ forces between nucleons are not equal and charge dependent.
$B$. In a nuclear reactor,the fission reaction will be in an accelerating state if the value of the neutron reproduction factor $k > 1$.

The figure shows three resistor configurations $R_1, R_2$,and $R_3$ connected to a $3\,V$ battery. If the power dissipated by the configurations $R_1, R_2$,and $R_3$ is $P_1, P_2$,and $P_3$ respectively,then:

If the plane $3x - 2y - z - 18 = 0$ meets the coordinate axes at $A$, $B$, and $C$, then the centroid of $\triangle ABC$ is:

The dispersive powers of the materials of two lenses forming an achromatic combination are in the ratio of $4: 3$. If the effective focal length of the two lenses is $+60 ~cm$,then the focal lengths of the lenses should be:

The potential difference between two parallel plates is $10^4 ~V$. If the plates are separated by $0.5 ~cm$,the force on an electron between the plates is