AIPMT 2012 Preliminary Mock Test

The potential energy of a particle in a force field is $U=A/r^2-B/r$, where $A$ and $B$ are positive constants and $r$ is the distance of particle from the centre. For stable equilibrium the distance of the particle is:

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be:

In the circuit shown the cells $A$ and $B$ have negligible resistances. For $V_A=12\text{V},R_1=500\Omega$ and $R=100\Omega$ the galvanometer ($G$) shows no deflection. The value of $V_B$ is:

Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be $3.57\text{V}$. The threshold frequency of the material is:

A mixture consists of two radioactive materials $A_1$ and $A_2$ with half-lives of $20\text{s}$ and $10\text{s}$ respectively. Initially the mixture has $40\text{g}$ of $A_1$ and $160\text{g}$ of $A_2$. The amount of the two in the mixture will become equal after: