The ratio of speed of an electron in the ground state in the Bohr's first orbit of hydrogen atom to velocity of light $$(c)$$ is ( $$h=$$ Planck's constant, $$\varepsilon_0=$$ permittivity of free space, $$e=$$ charge on electron)

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 [$$\cos 60^{\circ}=0.5$$]