IB Physics HL D 1 4 Gravitational Field Strength Questions

Practise IB Physics HL D.1.4 by solving gravitational-field strength, vector-superposition, orbital and multi-body problems.

Exam points

Solve gravitational-field magnitude and vector-superposition problems for multiple masses.
Relate field strength to orbital motion, radius, density and planetary data.
Evaluate gravitational-field models at points between bodies and in extended systems.

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Study D.1.4—Gravitational field strength conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 3]

This question is in two parts

In a simple model of the hydrogen atom, the electron is regarded as being in a circular orbit about the proton. The magnitude of the electric field strength at the electron due to the proton is $E_{\mathrm{p}}$ . The magnitude of the gravitational field strength at the electron due to the proton is $g_{\mathrm{p}}$ .

Determine the order of magnitude of the ratio shown below.

\frac{E_{\mathrm{p}}}{g_{\mathrm{p}}}

$E_{\mathrm{p}}=\frac{e}{4 \pi \varepsilon_{0} r^{2}}$ and $g_{\mathrm{p}}=\frac{G m_{\mathrm{p}}}{r^{2}}$ ; (both needed)
$\frac{e}{4 \pi \varepsilon_{0} G m_{\mathrm{p}}}\left(=\frac{9 \times 10^{9} \times 1.6 \times 10^{-19}}{6.7 \times 10^{-11} \times 1.7 \times 10^{-27}}\right) ;$ $\approx 10^{28}$ ;

Marking guidance:

Award [2 max] if response calculates ratio of force as this is an ECF from the first marking point ( $10^{39}$ ).
Award [3] for solution that correctly evaluates field strengths separately and then divides.

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IB Physics HL D 1 4 Gravitational Field Strength Questions question 1