Calcualte the energy associated with the first f `He^(+)`. What is the radius of this orbit?

A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad s^-1 . The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis?

What sort of energy is associate with a bird flying in air?

Estimate the frequency associated with a photon of energy 2eV.

Calculate the de Broglies wavelength associated with the electron revolving in the first excited state of hydrogen atom. The ground state energy of the hydrogen atom is -13.6 eV.

Calculate the radius of third orbit of hydrogen atom. Compare it with the same radius of second Bohr orbit of singly ionised helium atom.