A charge $$q$$ moves with velocity $$v$$ through electric field $$\mathrm{E}$$ as well as magnetic field (B). Then, the force acting on it is

The force acting on the electrons in hydrogen atom (Bohr's theory) is related to the principle quantum number $$n$$ as

A body of mass $$2 \mathrm{~kg}$$ is acted upon by two forces each of magnitude $$1 \mathrm{~N}$$ and inclined at $$60^{\circ}$$ with each other. The acceleration of the body in $$\mathrm{m} / \mathrm{s}$$ is [$$\cos 60^{\circ}=0.5$$]

Two rods of same material and volume having circular cross-section are subjected to tension $$T$$. Within the elastic limit, same force is applied to both the rods. Diameter of the first rod is half of the second rod, then the extensions of first rod to second rod will be in the ratio