The kinetic energy of a moving electron is 180 eV, its linear momentum is about: (mass of 1 electron = \( 9\times10^{-31}\,\mathrm{kg} \))
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 7.2\times10^{-24}\,\mathrm{kg\,m\,s^{-1}} \)
For a particle of mass m and kinetic energy K, \( K = \frac{p^{2}}{2m} \), so \( p = \sqrt{2mK} \). First convert the energy to joules.
\( K = 180\,\mathrm{eV} = 180\times1.6\times10^{-19}\,\mathrm{J} = 2.88\times10^{-17}\,\mathrm{J} \)
\( p = \sqrt{2\times9\times10^{-31}\times2.88\times10^{-17}} \)
\( p = \sqrt{5.184\times10^{-47}} = \sqrt{51.84\times10^{-48}} \)
\( p = 7.2\times10^{-24}\,\mathrm{kg\,m\,s^{-1}} \)