Wave-Particle Duality of Matter

In nuclear reactors, neutrons travel with energies of $5\times {10}^{-21} \mathrm{J}$. Find their speed and wavelength.

What is the speed of a proton having de Broglie wavelength of $0.08 \stackrel{\mathrm{o}}{\mathrm{A}}$?

Two particles have the same de Broglie wavelength and one is moving four times as fast as the other. If the slower particle is an $\mathrm{\alpha }$-particle, what are the possibilities for the other particle?

The equation $\mathrm{E}=\mathrm{pc}$ is valid

On what scale or under which circumstances is the wave nature of matter apparent?

The expression $\mathrm{p}=\frac{\mathrm{E}}{\mathrm{c}}$ defines the momentum of a photon. Can this expression be used for momentum of an electron or proton?