Tag: physics

Questions Related to physics

Two block of mass $10 kg$ and $20kg$ is separated by a distance $100 km$. What is the gravitational field (F) if $G=6.674 08 \times  10^{-11} m^3 kg^{-1} s^{-2}$?

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. $13.34 \times 10^{-16} N$

  2. $1.334 \times 10^{-11} N$

  3. $ 1334 \times 10^{-16} N$

  4. $1.334 \times 10^{-18} N$

Show answer
Correct Option: D
Explanation:
Given : $m _1 = 10kg$  $m _2 = 20 kg$  $r =10^5 m$
Gravitational force between the blocks $F = \dfrac{G m _1 m _2}{r^2}$
$\therefore$ $F = \dfrac{6.67408 \times 10^{-11} \times 10\times 20}{(10^5)^2}$
$\implies$ $1.334 \times 10^{-18} N$

If the radius of the earth were to shrink and its mass were to remain the same, the acceleration due to gravity on the surface of the earth with?

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. Increase

  2. Decrease

  3. Remains same

  4. Zero

Show answer
Correct Option: A
Explanation:

Gravitational force between two masses = $\quad K\dfrac { m1m2 }{ { r }^{ 2 } } \quad \quad $

Where

K is universal gravitational constant $m _1$ and $m _2$ are the masses $r$ is the distance between the masses.

Now , the acceleration due to $ m1 $ being earth will be = $ K\dfrac { m1 }{ { r }^{ 2 } } \quad \quad $

If the radius decreases and the mass remains same the acceleration will increase.

What is the gravitational field strength at the surface of Jupiter (mass $1.9\times 10^{27} kg$, radius $7.1\times 10^7 m$?

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. $25 N kg^{-1}$

  2. $25 N kg^{-2}$

  3. $35 N kg^{-1}$

  4. $55 N kg^{-2}$

Show answer
Correct Option: A
Explanation:

Gravitational field = $ K\dfrac { m1 }{ { r }^{ 2 } } \quad $

where $K$ is universal gravitational constant $m _1$ is the mass $r$ is the distance. 

G= $ 6.67\times { 10 }^{ -11 }\dfrac { 1.9({ 10 }^{ 27 }) }{ { (7.1\times { 10 }^{ 7 }) }^{ 2 } } \quad \quad $ 

   =  $\quad 25N{ kg }^{ -1 }\quad $

Both earth and moon are subject to the gravitational force to the sun. As observed from the sun, the orbit of the moon 

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. will be elliptical.

  2. will not be strictly elliptical because the total gravitational force on it is not central.

  3. is not elliptical but will necessarily be closed curve.

  4. deviates considerably from being elliptical due to influence of plants other than earth.

Show answer
Correct Option: B
Explanation:

If the moon were to experience only the gravitation of the earth only then the path would have been elliptical but in the present case moon experience the gravitational force of sun as well which distorts the path.

The fours basic forces in nature are.
I. Gravitational force
II. Electromagnetic force
III. Strong nuclear force
IV. Weak nuclear force
The relative magnitudes of these forces are in the order of.

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. III $>$ II $>$ I $>$ IV

  2. III $>$ II $>$ IV $>$ I

  3. I $>$ II $>$ III $>$ IV

  4. III $>$ I $>$ II $>$ IV

Show answer
Correct Option: B
Explanation:
Actually the order of the four basic forces in nature in order of their relative magnitudes are strong nuclear force $>$ Electromagnetic force $>$ Weak nuclear force $>$ Gravitational force.

Read the following statements.
I. A magnetic field is unable to penetrate into a superconductor.
II. An electric field can be cut off by a screen of conducting material
III. Gravitational field can be freely transmitted through all bodies
Which statement is false?

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. III

  2. II

  3. I

  4. None of these

Show answer
Correct Option: D
Explanation:

A. stronout feels weightless inside an artificial satellite because nothing is stopping their fall due to force of gravity.

Three particles each of mass m are kept at verticles of an equilateral triangle of side L. The gravitational field at centre due to these particle is:

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. Zero

  2. $\frac{3GM}{L^2}$

  3. $\frac{9GM}{L^2}$

  4. $\frac{12}{\sqrt{3}}\frac{GM}{L^2}$

Show answer
Correct Option: A
Explanation:

We know that for an equilateral triangle the line joining the center of gravity to each vertex of the triangle are each at angle $120^0$ and we also know that the field by each mass will be along these lines joining the center and vertex.

Also as the triangle is equilateral so all the vertex will be at same distance from the center, so the filed produced by each mass will be same.
Now as the field produced are eqaul in magnitude and at angle $120^0$ so 
net field will be $zero.$

The gravitational field lines are

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. Directed inwards towards a particle

  2. Directed outwards from a particle

  3. Directed along the particle's motion

  4. Directed perpendicular to the particle's motion

Show answer
Correct Option: A
Explanation:

The gravitational field lines are directed inwards towards a particle because at any point on the earth's field, a body will feel a force directed towards the center of the earth. The field lines becomes more spread out as the distance form the earth increases, which indicates the diminishing strength of the field

Two masses m and  100m are kept at points A and B. The gravitational field lines

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. Will be crowded at A than B

  2. Will be crowded at B than A

  3. Will be crowded equally at A and B

  4. Diverge from both the masses

Show answer
Correct Option: B
Explanation:

The strength of a gravitational field is given by the number of lines crowding at a point. This field strength is given by $GM/R^2$. Thus, it is proportional to the mass of the object

Larger the mass, more the field intensity and hence the number of lines of forces

Thus, the correct option is (b)

The field strength for a planet A of mass M and radius R is F. In another planet, the density is found to be 27 times the density of the planet A and the radius of the new planet is one third of A. Then,

physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

  1. Number of lines of force in both A and B are same

  2. Number of lines of force in A is more than B

  3. Number of lines of force in B is more than A

  4. Number of lines of force cannot be determined with this information

Show answer
Correct Option: A
Explanation:

Number of lines of force is given by the flux $\phi=\int (g.dA)=(GM/R^2)4 \pi R^2 = 4 \pi GM$

Thus, number of lines of forces is proportional to M. 

So, $M _A= \rho (4 \pi R^3)/3$ AND $M _B=27 \rho (4 \pi [R/3]^3)/3=\rho (4 \pi R^3)/3$

The mass of both the planets are same AND hence the flux is also same for both the planets

The correct option is (a)