Question
At what separation should two equal charges, 1.0C each, be placed so that the force between them equals the weight of a 50kg person?
✓
Answer
Given:
Magnitude of charges, $\text{q}_1=\text{q}_2=1\text{C}$
Electrostatic force between them,
F = Weight of a 50kg person
$\text{mg}=50\times9.8=490\text{N}$
$\text{mg}=490\text{N}$
Let the required distance be r.
By Coulomb's Law, electrostatic force,
$\text{F}=\frac{1}{4\pi\in_0}\frac{\text{q}_1\text{q}_2}{\text{r}^2}$
$\Rightarrow490=\frac{9\times10^9\times1\times1}{\text{r}^2}$
$\Rightarrow\text{r}^2=\frac{9\times10^9}{490}$
$\Rightarrow\text{r}=\sqrt{\frac{9}{49}\times10^8}$
$=\frac{3}{7}\times10^4\text{m}$
$=4.3\times10^3\text{m}$
Magnitude of charges, $\text{q}_1=\text{q}_2=1\text{C}$
Electrostatic force between them,
F = Weight of a 50kg person
$\text{mg}=50\times9.8=490\text{N}$
$\text{mg}=490\text{N}$
Let the required distance be r.
By Coulomb's Law, electrostatic force,
$\text{F}=\frac{1}{4\pi\in_0}\frac{\text{q}_1\text{q}_2}{\text{r}^2}$
$\Rightarrow490=\frac{9\times10^9\times1\times1}{\text{r}^2}$
$\Rightarrow\text{r}^2=\frac{9\times10^9}{490}$
$\Rightarrow\text{r}=\sqrt{\frac{9}{49}\times10^8}$
$=\frac{3}{7}\times10^4\text{m}$
$=4.3\times10^3\text{m}$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
It is desirable that the standards of units be easily available, invariable, indestructible and easily reproducible. If we use foot of a person as a standard unit of length, which of the above features are present and which are not?
Work function of sodium is 2.3eV. Does sodium show photoelectric emission for light of wavelength $6800\mathring{\text{A}}?$
→A beam of electrons enters crossed region of electric field of intensity $E$ and magnetic field of intensity B. For what speed of electrons, the electron beam will remain unaffected?
→Light falls from glass $(\mu=1.5)$ to air. Find the angle of incidence for which the angle of deviation is 90°.
→Write the truth table for the combination of the gates shown. Name the gates used.
A steady current (I1) flows through a long straight wire. Another wire carrying steady current (I2) in the same direction is kept close and parallel to the first wire. Show with the help of a diagram how the magnetic field due to the current I1 exerts a magnetic force on the second wire. Write the expression for this force.
Explain the terms ‘depletion layer’ and ‘potential barrier’ in a p-n junction diode. How are the (a) Width of depletion layer, and (b) Value of potential barrier affected when the p-n junction is forward biased?
At what rate should the earth rotate so that the apparent g at the equator becomes zero? What will be the length of the day in this situation?
An electron is accelerated through a potential difference of 100 volts. What is the de-Broglie wavelength associated with it? To which part of the electromagnetic spectrum does this value of wavelength correspond?
The potential difference across the terminals of a battery of emf 12V and internal resistance $2\Omega$ drops to 10V when it is connected to a silver voltameter. Find the silver deposited at the cathode in half an hour. Atomic weight of silver is 107.9g/mole.
→