Which fundamental interaction acts between ordinary masses?

Do two positive charges attract or repel?

If the separation in an inverse-square force doubles, what happens to the force magnitude?

A charge \(q=3.0\,\mu\mathrm{C}\) is placed in an electric field of \(200\,\mathrm{N\,C^{-1}}\). Find the force magnitude.

Using \(G=6.67\times10^{-11}\,\mathrm{N\,m^2\,kg^{-2}}\), find the gravitational force between \(2.0\,\mathrm{kg}\) and \(5.0\,\mathrm{kg}\) masses separated by \(0.50\,\mathrm{m}\).

Using \(k=8.99\times10^9\,\mathrm{N\,m^2\,C^{-2}}\), find the electric force magnitude between \(+2.0\,\mu\mathrm{C}\) and \(-3.0\,\mu\mathrm{C}\) charges separated by \(0.20\,\mathrm{m}\). State whether it is attractive or repulsive.

In a gravitational inverse-square model, one mass is tripled and the separation is doubled. By what factor does the force change?

A charge \(q=-4.0\,\mu\mathrm{C}\) is in a uniform field \(\vec{E}=150\hat{\imath}\,\mathrm{N\,C^{-1}}\). Find \(\vec{F}\).

Which fundamental interaction is responsible for beta decay, and which one helps bind nuclei together?

For two objects with masses \(m_1,m_2\), charges \(q_1,q_2\), and the same separation \(r\), derive \(\frac{F_E}{F_g}\), then state explicitly why it is independent of \(r\).

For two protons separated by any distance \(r\), estimate \(\frac{F_E}{F_g}\) using \(k=8.99\times10^9\), \(G=6.67\times10^{-11}\), \(e=1.60\times10^{-19}\,\mathrm{C}\), and \(m_p=1.67\times10^{-27}\,\mathrm{kg}\). Then estimate \(\frac{F_E}{F_g}\) for an electron-proton pair and compare.

A particle of mass \(m\) and charge \(q\) is held at rest in a uniform gravitational field \(\vec{g}\) by a uniform electric field \(\vec{E}\). Derive \(\vec{E}\), then derive \(|q/m|\) needed for support for a given \(|\vec E|\), and state the field direction for positive and negative \(q\) near Earth's surface.