DP Physics (last assessment 2024)

Question 18M.2.HL.TZ2.9c.i

c.i.

[Maximum mark: 1]

18M.2.HL.TZ2.9c.i

(c.i)

Show that the speed v of an electron in the hydrogen atom is related to the radius r of the orbit by the expression

$v = \sqrt {\frac{{k{e^2}}}{{{m_{\text{e}}}r}}}$

where k is the Coulomb constant.

[1]

Markscheme

$\frac{{{m_{\text{e}}}{v^2}}}{r} = \frac{{k{e^2}}}{{{r^2}}}$

KE = $\frac{1}{2}$ PE hence $\frac{1}{2}$ m_ev² = $\frac{1}{2}\frac{{k{e^2}}}{r}$

«solving for v to get answer»

Answer given – look for correct working

[1 mark]

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