Tag: gravitation: planets and satellites

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Questions Related to gravitation: planets and satellites

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

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

  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.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

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

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 $g=9.8m\quad { s }^{ -1 }$)

  1. $11.2km\quad { s }^{ -1 }$
  2. $8km\quad { s }^{ -1 }$
  3. $3.2km\quad { s }^{ -1 }$
  4. $1.5km\quad { s }^{ -1 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $(C)$
Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Weightlessness occurs when the normal force is zero. At the center of the Earth, gravitational force is zero, but you are not in free fall in the same sense as an orbit; however, you would experience zero weight. Wait, actually, in a lift moving with uniform velocity, the acceleration is zero, so the normal force equals your weight (mg), meaning you feel your normal weight. Therefore, you do NOT experience weightlessness in a lift moving with uniform velocity.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

so that the correct option is A.

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

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.

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Both statements are true. An artificial satellite is in free fall, leading to weightlessness. On the Moon, you are standing on a surface, so the normal force balances the gravitational pull, meaning you feel weight. Statement 2 is a true statement, but it doesn't explain the reason for the difference in the sensation of weightlessness (which is about the presence of a normal force, not just the source of gravity).

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

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

  1. more weight

  2. lesser weight

  3. weightlessness

  4. nothing at all
Reveal answer Fill a bubble to check yourself
C Correct answer
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.


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

    Motion of artificial satellite around the earth is powered by :

    1. Liquid fuel

    2. Solar energy

    3. Atomic energy

    4. None of these
    Reveal answer Fill a bubble to check yourself
    D Correct answer
    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.

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

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

    1. greater than their real weight

    2. lesser than their real weight

    3. zero

    4. infinity
    Reveal answer Fill a bubble to check yourself
    C Correct answer
    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.