Gravitation vs. Electrostatics

Q. Four point charges Q, q, Q and q are placed at the corners of a square of side 'a' as shown in the figure. Q q

Find the
(a) resultant electric force on a charge Q and
(b) potential energy of this system.

Q. $F_g$ and $F_e$represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm. The ratio of $\frac{F_g}{F_e}$ is of the order of

1. ${10}^{-43}$
2. ${10}^{42}$
3. $10$
4. $1$

Q. The ratio of electrostatic and gravitational forces acting between electron and proton separated by a distance $5\times {10}^{-11}m$, will be (Charge on electron $=1.6\times {10}^{-19}C$, mass of electron $=9.1\times {10}^{–31}$ kg, mass of proton $=1.6\times {10}^{-27}kg,G=6.7\times {10}^{-11}N{m}^2/k{g}^2)$

1. $2.36\times {10}^{39}$
   
2. $2.34\times {10}^{41}$
   
3. $2.34\times {10}^{42}$
4. $2.36\times {10}^{40}$
   

Q. $F_g$ and $F_e$represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm apart. The ratio of $F_g$ and $F_e$ is of the order of

1. ${10}^{42}$
2. ${10}^{40}$
3. ${10}^{-43}$
4. $10$

Q. Two particle of equal mass m and charge q are placed at a distance of 16 cm. They do not experience any force. The value of $\frac{q}{m}$ is

1. $\sqrt{\frac{G}{4\pi {ϵ}_0}}$
   
2. l
3. $\sqrt{\frac{\pi {ϵ}_0}{G}}$
   
4. $\sqrt{4\pi {ϵ}_{0}G}$

Q. Assertion: The coulomb force is the dominating force in the universe.
Reason :The coulomb force is weaker than the gravitational force.

1. If both assertion and reason are true but reason is not the correct explanation of the assertion.
2. If the assertion and reason both are false.
3. If both assertion and reason are true and the reason is the correct explanation of the assertion.
4. If assertion is false but reason is true.
5. If assertion is true but reason is false.

Q. two identical pith balls , each carrying a charge q, are suspended from a common point by two strings of length l each.Find the mass of each ball if angle between two balls at equilibrium is 2theta

Q. Four charges of +q, -q, +q and +q are placed at the corners A, B, C and D of a square. The resultant force on the charge at D is

1. $\frac{q^2}{4\pi {ϵ}_0{a}^2}(\sqrt{2}-\frac{1}{2})$
2. $\frac{2q^2}{\pi {ϵ}_0{a}^2}$
3. $zero$
4. $\frac{q^2}{8\pi {ϵ}_0{a}^2}2\sqrt{2}$

Q. A charged particle moves with constant velocity in a region where no effect of gravity is felt but an electrostatic field $\overrightarrow{E}$ together with a magnetic field $\overrightarrow{B}$ may be present. Then which of the following cases are possible?

1. $\overrightarrow{E}\ne 0,\overrightarrow{B}\ne 0$
2. $\overrightarrow{E}\ne 0,\overrightarrow{B}=0$
3. $\overrightarrow{E}=0,\overrightarrow{B}=0$
4. $\overrightarrow{E}=0,\overrightarrow{B}\ne 0$

Q.

Why is gravitational force the weakest force in nature?

Q.

How do you find r in Coulombs Law?

Q.

The average separation between the proton and the electron in a hydrogen atom in ground state is $5.3\times {10}^{-11m}$ (a) Calculate the Coulomb force between them at this separation. (b) When the atom goes into its first excited state the average separation between the proton and the electron increases to four times its value in the ground state. What is the Coulomb force in this state?

Q.

What is the coulombs law in electrostatics?

Q. The distance between the electron and proton in hydrogen atom is $5.3\times {10}^{-11}m$. Determine the magnitude of the ratio of electrostatic and gravitational force between them.
Given me $=9.1\times {10}^{-31}kg,mp=1.67\times {10}^{-27}kg,e=1.6\times {10}^{-19}C$ and $G=6.67\times {10}^{-11}N{m}^{2}k{g}^{-2}$

Q. A particle with a charge 2μC is hanging in air above a similarly charged conducting surface whose surface charge density is $43.3\times {10}^{-12}C/m^2$. The mass of particle is

1. 1mg

2. 1g

3. 1 kg

4. 10^-2 kg

Q. $F_G$ and $F_e$ represents gravitational and electrostatic force respectively between electrons situated at a distane $10cm$. The ratio of $F_G/F_e$ is nearly of the order of

1. ${10}^{42}$
2. ${10}^{-34}$
3. $1$
4. ${10}^{-43}$

Q. Assertion :If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive. Reason: the electrostatic force is proportional to the charges contained by entities.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. Coulomb's law for electrostatic force between two point charges and Newton's law for gravitational force between two stationary point masses, both have inverse-square dependence on the distance between the charges/masses. (a) Compare the strength of these forces by determining the ratio of their magnitudes (i) for an electron and a proton and (ii) for two protons. (b) Estimate the accelerations of electron and proton due to the electrical force of their mutual attraction when they are $1\mathring{A}(={10}^{-10}m)$ apart? $(m_p=1.67\times {10}^{-27}kg,m_e=9.11\times {10}^{-31}kg)$

Q.

It was said gravity is the weakest force in existence..is it weaker than Vanderwaal’s force of attraction?

Q. Force acting on charges separated by some distance is shown in the figure.


Select the correct relation between given parameters :

1. $q_1{q}_2>0,{\overrightarrow{F}}_{12}\ne {\overrightarrow{F}}_{21}$
2. $q_1{q}_2<0,{\overrightarrow{F}}_{12}=-{\overrightarrow{F}}_{21}$
3. $q_1{q}_2<0,{\overrightarrow{F}}_{12}=-2{\overrightarrow{F}}_{21}$
4. $q_1{q}_2>0,{\overrightarrow{F}}_{12}=-{\overrightarrow{F}}_{21}$

Q.

If fish are flowing at a rate of 10 fish/$m^{2}s$, and the 10 $m^2$ net is dipped at an angle of ${60}^0$ in their path for 1 second, how many fish do we catch?

1. 50 √3

2. 50

3. 60

4. 100

Q.

Which of the following is not related to gravitational law?

1. Motion of planets around the earth

2. Rainfall

3. Snowfall

4. Thunder lightning

Q.

How far apart the two electrons be If the force between them equals the weight of an electron.

Q. 74.Two identical small bodies each if mass m and charge q are suspended from two strings each of length l from a fixed point.this whole system is taken into an orbiting artificial satellite, then find the tension in strings

Q. If $F_g$ and $F_e$ are gravitational and electrostatic forces between two electrons at a distance $0.1m$ then $F_g/F_e$ is in the order of

1. ${10}^{43}$
2. ${10}^{-43}$
3. ${10}^{35}$
4. ${10}^{-35}$

Q.

When the distance between the charged particles is halved, the force between them becomes

1. One-fourth

2. Half

3. Double

4. Four times

Q.

Two particles of mass 'm' and charge 'q' each are suspended by means of two silk threads of length 'l' each from the same point. If they are taken into an artificial satellite, the angle between the threads in equilibrium is

1. 0⁰

2. 60⁰

3. 90⁰

4. 180⁰

Q. An electron and a proton are accelerated through the same potential difference. The ratio of their de Broglie wavelengths ($\frac{{\lambda }_e}{{\lambda }_p}$ ) is

1. 1
2. $\frac{m_e}{m_p}$
3. $\frac{m_p}{m_e}$
4. $\sqrt{\frac{m_p}{m_e}}$

Q. 63.Two small balls having equal positive charge q on each are suspended by to install ating strings of equal length from I from a hook to a stand.The whole set up a take in a satellite into space where is no gravity what is the angle between two strings? 90 degree 180 degree 0 degree 45 degree

Q. The ratio of electrostatic and gravitational forces acting between electron and proton separated by a distance $5\times {10}^{-11}m$, will be (Charge on electron $=1.6\times {10}^{-19}C$, mass of electron $=9.1\times {10}^{–31}$ kg, mass of proton $=1.6\times {10}^{-27}kg,G=6.7\times {10}^{-11}N{m}^2/k{g}^2)$

1. $2.36\times {10}^{39}$
   
2. $2.36\times {10}^{40}$
   
3. $2.34\times {10}^{41}$
   
4. $2.34\times {10}^{42}$