$A$ $2 \, MeV$ proton is moving perpendicular to a uniform magnetic field of $2.5 \, T$. The force on the proton is

Assertion $(A)$: When a proton and a neutron enter into a transverse magnetic field with equal speeds,they trace circular paths of equal radii.
Reason $(R)$: In a transverse magnetic field,the period of revolution of a charged particle in a circular path is directly proportional to the mass of the particle.

$A$ proton, a deuteron, and an $\alpha$-particle are moving with the same momentum in a uniform magnetic field. The ratio of magnetic forces acting on them is.......... and their speeds are in the ratio of..........

An electron (mass $= 9 \times 10^{-31} \, kg$,charge $= 1.6 \times 10^{-19} \, C$) with a kinetic energy of $7.2 \times 10^{-18} \, J$ is moving in a circular orbit in a magnetic field of $9 \times 10^{-5} \, Wb/m^2$. The radius of the orbit is ..... $cm$.

$A$ proton is moving along the $Z$-axis in a magnetic field. The magnetic field is along the $X$-axis. The proton will experience a force along

$A$ particle having charge $q$ enters a region of uniform magnetic field $\vec{B}$ (directed inwards) and is deflected a distance $x$ after travelling a distance $y$. The magnitude of the momentum of the particle is: