Tag: gravitation: planets and satellites

Questions Related to gravitation: planets and satellites

WEIGHTLESSNESS
An astronaut experiences weightlessness in a space satellite. It is because

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. the gravitational force is small at that location in space.

  2. the gravitational force is large at that location in space.

  3. the astronaut experiences no gravity.

  4. the gravitational force is infinitely large at that location in space.

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Correct Option: C
Explanation:

An astronaut experiences weightlessness in a space satellite. It is because the astronaut experiences no gravity.

A spaceship is launched into a circular orbit close to earth's surface. The additional velocity that should be imparted to the spaceship in the orbit to overcome the gravitational pull is:
(Radius of earth $=6400km$ and $g=9.8m\quad { s }^{ -1 }$)

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. $11.2km\quad { s }^{ -1 }$

  2. $8km\quad { s }^{ -1 }$

  3. $3.2km\quad { s }^{ -1 }$

  4. $1.5km\quad { s }^{ -1 }$

Show answer
Correct Option: C
Explanation:
Given,
Radius of the earth, $R=6400km$
Acceleration due to gravity, $g=9.8m/s^2$
When a satellite is orbitting the earth its velocity is its orbital velocity given by orbital velocity: 
 ${ V } _{ 0 }=\sqrt { \dfrac { GM }{ R }  } =\sqrt { g } R$    $[\because g =\frac{GM}{R^2}]$
If it has to overcome gravitational pull then its velocity should be escape velocity escape velocity ${ V } _{ e }=\sqrt { \dfrac { 2GM }{ r }  } =\sqrt { 2gR } $
Additional velocity required is $V={ V } _{ e }-{ V } _{ 0 }=\sqrt { 2gR } -\sqrt { gR } =\sqrt { gR } \left( \sqrt { 2 } -1 \right) $
given that $R=64004m=64\times { 10 }^{ 6 }m$
$g=9.8m/{ s }^{ 2 }$
So, additional velocity will be:
$V=\sqrt { gR } \left( \sqrt { 2 } -1 \right) =\sqrt { 9.8\times 6.4\times { 10 }^{ 6 } } \left( \sqrt { 2 } -1 \right) $
$\Rightarrow V=3.28\times { 10 }^{ 3 }m/s$
Hence, the correct option is $(C)$

Astronauts on the orbiting space station are weightless because...

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. there is no gravity in space and they do not weigh anything.

  2. space is a vacuum and there is no gravity in a vacuum.

  3. space is a vacuum and there is no air resistance in a vacuum.

  4. None of the reasons given above are correct

Show answer
Correct Option: D
Explanation:

As the astronauts are in a frame which is rotating around the earth and the centripetal acceleration on astronauts and the satellite is $same$, $g=GM/r^2$ where $r$ is the radius of the orbit. So relative to the satellite the astronauts can't exert any force on satellite so no reaction force from the satellites so they feel the condition of weightlessness.


Its same like an elevator falling from top to ground freely $cable$ broken.

So the man in the elevator and the elevator have same acceleration $g$ so the man can't exert any force on the elevator so the condition of weightlessness.

Option D is correct.

In which of the following situations, you will not experience weightlessness?

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. If you are at the center of the earth

  2. You are falling freely under gravity of the earth

  3. Inside a spacecraft which is in an orbit around the earth

  4. In a lift moving downwards with uniform velocity

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Correct Option: A

An astronaut,inside an earth`s satellite experiences weightlessness because

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. he is falling freely

  2. no external force is acting on it

  3. no reaction is exerted by the floor of the satellite

  4. he is far away from the earth`s surface

Show answer
Correct Option: A
Explanation:

An astronaut,inside an earth`s satellite experiences weightlessness because he is falling freely.

so that the correct option is A.

Statement -1 :- A person feels weightlessness in an artificial satellite of the Earth. However a person on the Moon (natural satellite) feels his weight.
 and
 Statement - 2 :- Artificial satellite is a freely falling body and on the Moon surface, the weight is mainly due to Moon's gravitational attraction.

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for statement-1

  2. Statement-1 is True, Statement-2 is True; Statement-2 is not a correct explanation for statement-1

  3. Statement-1 is true, Statement -2 is False

  4. Statement-1 is true, Statement -2 is True

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Correct Option: B

While orbiting around the earth in a apaceship, an astronaut experiences

physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

  1. more weight

  2. lesser weight

  3. weightlessness

  4. nothing at all

Show answer
Correct Option: C
Explanation:

  • When an astronaut is orbiting the earth, he is in a state of free fall along with the space vehicle, hence the astronaut is not able to exert his mass on its surface. This condition is called weightlessness condition.
  • Hence,option C is correct.


    • Motion of artificial satellite around the earth is powered by :

    physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

    1. Liquid fuel

    2. Solar energy

    3. Atomic energy

    4. None of these

    Show answer
    Correct Option: D
    Explanation:

    Answer is D.

    The orbit of an artificial earth satellite is an ellipse whose focus is at the center of the earth (in a particular case, a circle) and which maintains an unchanged position in space. Movement along such an orbit is called undisturbed motion and proceeds on the assumption that the earth attracts, according to Newtons law, like a sphere with spherical density distribution and that the satellite is affected only by the earths gravitational attraction.
    Such factors as atmospheric drag, compression of the earth, solar radiation pressure, and the attraction of the moon and sun are the reasons for deviations from undisturbed motion. Because of atmospheric drag, satellites in orbits at altitudes of several hundred kilometers gradually descend and, entering the dense layers of the atmosphere at an altitude of 120130 km and lower, disintegrate and burn up; thus, they exist for a limited period.
    Hence, the m    otion of artificial satellite around the earth is NOT powered by any of the options given.

    Which of the following is the cause of weightlessness experienced while orbiting around earth on a spaceship ?

    physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

    1. Inertia

    2. Zero gravity

    3. Acceleration

    4. Centre of gravity

    Show answer
    Correct Option: B
    Explanation:

    Weight of a body is due to its weight. A body becomes weightless when effective gravity on the body is zero.

    While orbiting around the earth in a spaceship, an astronaut weight becomes

    physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

    1. greater than their real weight

    2. lesser than their real weight

    3. zero

    4. infinity

    Show answer
    Correct Option: C
    Explanation:

    In a spaceship the astronaut weighs zero. Since there is no gravity in the space person feels weightless. Apart from these space is a vacuum and there is no air resistance and thus we feel weightless.