5.3 Coulomb's law  (Page 5/11)

In a salt crystal, the distance between adjacent sodium and chloride ions is $2.82\times {10}^{\mathrm{-10}}\text{m}.$ What is the force of attraction between the two singly charged ions?

Protons in an atomic nucleus are typically ${10}^{\mathrm{-15}}\text{m}$ apart. What is the electric force of repulsion between nuclear protons?

Suppose Earth and the Moon each carried a net negative charge − Q . Approximate both bodies as point masses and point charges.

(a) What value of Q is required to balance the gravitational attraction between Earth and the Moon?

(b) Does the distance between Earth and the Moon affect your answer? Explain.

(c) How many electrons would be needed to produce this charge?

Point charges $q_1=50\mu \text{C}$ and $q_2=\mathrm{-25}\mu \text{C}$ are placed 1.0 m apart. What is the force on a third charge $q_3=20\mu \text{C}$ placed midway between $q_1$ and $q_2$ ?

Where must $q_3$ of the preceding problem be placed so that the net force on it is zero?

Two small balls, each of mass 5.0 g, are attached to silk threads 50 cm long, which are in turn tied to the same point on the ceiling, as shown below. When the balls are given the same charge Q , the threads hang at $5.0\text{°}$ to the vertical, as shown below. What is the magnitude of Q ? What are the signs of the two charges?

Point charges $Q_1=2.0\mu \text{C}$ and $Q_2=4.0\mu \text{C}$ are located at ${\overrightarrow{\text{r}}}_1=(4.0\widehat{\text{i}}-2.0\widehat{\text{j}}+5.0\widehat{\text{k}})\text{m}$ and ${\overrightarrow{\text{r}}}_2=(8.0\widehat{\text{i}}+5.0\widehat{\text{j}}-9.0\widehat{\text{k}})\text{m}$ . What is the force of $Q_2$ on $Q_1$ ?

The net excess charge on two small spheres (small enough to be treated as point charges) is Q . Show that the force of repulsion between the spheres is greatest when each sphere has an excess charge Q /2. Assume that the distance between the spheres is so large compared with their radii that the spheres can be treated as point charges.

Two small, identical conducting spheres repel each other with a force of 0.050 N when they are 0.25 m apart. After a conducting wire is connected between the spheres and then removed, they repel each other with a force of 0.060 N. What is the original charge on each sphere?

A charge $q=2.0\mu \text{C}$ is placed at the point P shown below. What is the force on q ?

What is the net electric force on the charge located at the lower right-hand corner of the triangle shown here?

Two fixed particles, each of charge $5.0\times {10}^{\mathrm{-6}}\text{C},$ are 24 cm apart. What force do they exert on a third particle of charge $\mathrm{-2.5}\times {10}^{\mathrm{-6}}\text{C}$ that is 13 cm from each of them?

The charges $q_1=2.0\times {10}^{\mathrm{-7}}\text{C,}{q}_2=\mathrm{-4.0}\times {10}^{\mathrm{-7}}\text{C,}$ and $q_3=\mathrm{-1.0}\times {10}^{\mathrm{-7}}\text{C}$ are placed at the corners of the triangle shown below. What is the force on $q_1?$

What is the force on the charge q at the lower-right-hand corner of the square shown here?

Point charges $q_1=10\mu \text{C}$ and $q_2=\mathrm{-30}\mu \text{C}$ are fixed at $r_1=\left(3.0\widehat{\text{i}}-4.0\widehat{\text{j}}\right)\text{m}$ and $r_2=\left(9.0\widehat{\text{i}}+6.0\widehat{\text{j}}\right)\text{m}.$ What is the force of $q_2\text{on}{q}_1$ ?