Class 11 Exam > Class 11 Videos > Earths satellite - Gravitation
Earths satellite - Gravitation Video Lecture - Class 11
FAQs on Earths satellite - Gravitation Video Lecture - Class 11
| 1. What is Earth's satellite? |  |
Ans. Earth's satellite refers to the celestial body that orbits around the Earth. It is commonly known as the Moon. The Moon is the only natural satellite of Earth and plays a significant role in various aspects such as tides, lunar cycles, and even cultural beliefs.
| 2. How does the Moon's gravitational force affect Earth? | |
Ans. The Moon's gravitational force affects Earth in several ways. Firstly, it creates tidal effects, causing the rise and fall of ocean tides. Secondly, it stabilizes Earth's axial tilt, which is crucial for maintaining stable seasons on our planet. Additionally, the Moon's gravity also influences the Earth's rotation, although the effect is relatively small.
| 3. What is the significance of studying Earth's satellite? | |
Ans. Studying Earth's satellite, the Moon, is of great significance for various reasons. It helps scientists understand the formation and evolution of the Moon itself, as well as its relationship with Earth. Furthermore, studying the Moon provides valuable insights into the formation of other celestial bodies and the entire solar system. It also aids in unraveling the mysteries of the universe and expanding our knowledge of space exploration.
| 4. How does the Moon's gravitational force impact human activities on Earth? | |
Ans. The Moon's gravitational force has a minimal direct impact on human activities on Earth. However, it indirectly influences activities such as fishing and navigation through its tidal effects. Additionally, the Moon's gravitational pull has historically played a role in cultural beliefs, myths, and even calendar systems. Moreover, the Moon's presence in the night sky offers aesthetic beauty and inspiration to people across the world.
| 5. Can the Moon's gravitational force change over time? | |
Ans. Yes, the Moon's gravitational force can change over time, but the change is relatively slow. The primary factor responsible for this change is the interaction between the Moon and Earth, which causes a transfer of angular momentum. As a result, the Moon moves away from Earth at an average rate of about 3.8 centimeters per year. This gradual increase in distance affects the strength of the Moon's gravitational force, albeit in a minimal manner.
Text Transcript from Video
hello friends this video on gravitation
part 16 is brought to you by exam fear
calm no more fear from exam please make
sure that you have watched all the
videos from part 1 to 15 before going
ahead with path 16 leave earth
satellites what is an earth satellite
any object revolving around the earth is
termed as Earth satellite for that
matter
can we talk of the term satellite it
would mean any object which is revolving
around a planet so when I say earth
satellite it would mean objects
revolving around the earth now we can
classify satellites into two types one
is natural satellite the other one is
artificial satellite so here we'll see
what is a natural satellite natural
satellite is a satellite which existed
already in nature on its own
that means nobody had to put in any
efforts to discover that satellite it
was already there on its own so the only
natural satellite which earth has is
moon so moon is the only natural Earth
satellite which existed on its phone and
which revolves around the earth now let
us have a look at artificial satellite
so artificial satellites are human built
objects orbiting the earth for practical
uses so this means that human beings
develop certain type of objects which
are capable of revolving around the
earth
now when human beings take so much of
pain in developing such artificial
satellites so obviously they have
certain practical purposes because of
which they acted so there are several
purposes which these artificial
satellite cells we will see that so it
is something like this let us suppose if
this is an artificial satellite it
revolves around the earth in a fixed
orbit so there are various uses of
artificial satellites like it is used
for communication for television
broadcasts weather observation military
support
when needed navigation and scientific
research of course so because of so many
different purposes different artificial
satellites are built by human beings so
till now we saw what is an earth
satellite what are the two types of
earth satellites natural and artificial
now we will go ahead and we'll see how
to determine the time period of an earth
satellite so we will try to get an
expression for determining the time
period that is the time a satellite
takes to complete one rotation around
the earth let us suppose this is the
earth and we have a satellite which
revolves around the earth in a circular
orbit so in this case since it moves in
a circular orbit there could be a
centripetal force which would be acting
on it now what would be the centripetal
force the centripetal force will be MV
square divided by R but will be I I will
be nothing but r e + h h would be the
distance of the satellite from the
surface of the earth because our e is
the radius of the earth now the
satellite would be somewhere at some
point say this so this distance will
again be H so the entire distance would
become R e + H right so this centripetal
force will act towards the center fine
now there would be another gravitational
force which would act between the
satellite and the earth so that will be
given by G into M that is mass of the
satellite Capital m V that is mass of
the earth divided by r e + H whole
square now this is the force which will
balance the centripetal force F C so
therefore these two forces should be
equal that is FC should be equal to F G
now let us equate both the forces so it
will become MD
square divided by re plus h is equal to
G M mg divided by R + H whole square
right so this RT plus h and this re + H
will get cancelled this m and this M
will also get cancelled so we get V
square is equal to g m-e / r e plus h so
we get from this p is equal to root over
2 root over g m-e divided by r e plus h
so this would be the velocity with which
the satellite would be revolving around
the earth so this would be the velocity
now we want to calculate the time period
right so we will do that now we know
that the satellite would cover 2 pi r e
plus h that is the circumference right 2
pi r t + H distance with speed V with
speed V which we calculated just now
therefore the time period would be equal
to 2 pi r e + h that is the total
distance traveled divided by the
velocity v so this will be equal to 2 pi
r e + h divided by root over g m-e into
root over r-e + h i have just put the
value of v from the previous equation
which we got in the previous slide
therefore value of t comes out to be 2
pi r e plus h to the power 3 by 2
divided by root over g m-e so this is
nothing but the time period of our
satellite which revolves around the
ugh so this is how we calculate the
velocity of a satellite with which it
revolves around the earth as well as the
time period of the satellite with which
it orbits around the earth now we will
also consider a special case of this so
we will see a special case a special
case when H that is the height which we
consider it like if suppose this is the
earth and this is your satellite so this
is radius of the earth and this
distances H if we say that H is very
very less than R T what will happen in
that case in that case R a plus h can be
approximated to R T because H is very
small when compared to a T so T will be
equal to 2 pie root over r-e cube
divided by g m-e now this we can write
in terms of acceleration due to gravity
as root over r-e divided by G because G
is equal to g m-e by are in spread so
using that we can write this so this
will become the time period in case of
in case H is very very less than Rd that
means if the satellite is very close to
the surface of the earth so in that case
we will arrive at this solution so you
saw how do we calculate the time period
for a satellite as well as the velocity
with which the satellite moves around
the planet now we will go ahead and we
will see the energy of an orbiting
satellite now we will find out an
expression to evaluate the energy of an
orbiting satellite before this we saw
how to calculate the time period and
velocity of a satellite which is
orbiting around the earth now we will
see how do we evaluate the energy of an
orbiting satellite now let us suppose
that for the
at late we consider that M is the mass
of the satellite and the velocity with
which it is moving around the earth is V
so M is mass velocity is V so what would
be the kinetic energy of the satellite
it would be half M field square now we
have already found out the value of V
just in the previous topic so V is
nothing but g m-e divided by r e plus h
so we get the kinetic energy as half m g
m e / r e plus h now let us calculate
the potential energy so what would be
the potential energy it would be minus g
m-e into m / r e plus h now if you see
the values of kinetic energy and
potential energy you can find out the
total value of energy that is total
energy is nothing but kinetic energy
plus potential energy so if you
calculate that it is half m g into m e /
r e + h + - g m-e so + - would be - so -
g m-e into m / r e plus h so this comes
out to be minus g m-e into m / r e + h
so this is the value of total energy
right so what do we observe from this we
observe the conclusion first conclusion
is we find we found that potential
energy is equal to so we found that
potential energy is equal to twice the
value of kinetic energy if you see the
value of potential energy you can very
clearly see that half of potential
energy is kinetic energy right and what
is the second conclusion the total
energy is negative that means so that
meant when the total energy is negative
that means this is
is a bound system that means the system
cannot escape so this shows that this is
our earth later suppose and this is the
satellite since the total energy is
negative therefore the satellite is
bound to this earth satellite system and
it is moving in this fashion otherwise
it would have just escaped from the
attraction pool of the earth and it
would have not moved in and particular
orbit so this also indicates from the
fact that total energy has a negative
sign now we'll go ahead and look at
certain problems regarding all the
topics which we have studied so far
thank you please visit exam vo comm to
watch free educational videos try free
online tests get the best quality study
materials study from the best tutors and
mentors and much more thank you once
again
part 16 is brought to you by exam fear
calm no more fear from exam please make
sure that you have watched all the
videos from part 1 to 15 before going
ahead with path 16 leave earth
satellites what is an earth satellite
any object revolving around the earth is
termed as Earth satellite for that
matter
can we talk of the term satellite it
would mean any object which is revolving
around a planet so when I say earth
satellite it would mean objects
revolving around the earth now we can
classify satellites into two types one
is natural satellite the other one is
artificial satellite so here we'll see
what is a natural satellite natural
satellite is a satellite which existed
already in nature on its own
that means nobody had to put in any
efforts to discover that satellite it
was already there on its own so the only
natural satellite which earth has is
moon so moon is the only natural Earth
satellite which existed on its phone and
which revolves around the earth now let
us have a look at artificial satellite
so artificial satellites are human built
objects orbiting the earth for practical
uses so this means that human beings
develop certain type of objects which
are capable of revolving around the
earth
now when human beings take so much of
pain in developing such artificial
satellites so obviously they have
certain practical purposes because of
which they acted so there are several
purposes which these artificial
satellite cells we will see that so it
is something like this let us suppose if
this is an artificial satellite it
revolves around the earth in a fixed
orbit so there are various uses of
artificial satellites like it is used
for communication for television
broadcasts weather observation military
support
when needed navigation and scientific
research of course so because of so many
different purposes different artificial
satellites are built by human beings so
till now we saw what is an earth
satellite what are the two types of
earth satellites natural and artificial
now we will go ahead and we'll see how
to determine the time period of an earth
satellite so we will try to get an
expression for determining the time
period that is the time a satellite
takes to complete one rotation around
the earth let us suppose this is the
earth and we have a satellite which
revolves around the earth in a circular
orbit so in this case since it moves in
a circular orbit there could be a
centripetal force which would be acting
on it now what would be the centripetal
force the centripetal force will be MV
square divided by R but will be I I will
be nothing but r e + h h would be the
distance of the satellite from the
surface of the earth because our e is
the radius of the earth now the
satellite would be somewhere at some
point say this so this distance will
again be H so the entire distance would
become R e + H right so this centripetal
force will act towards the center fine
now there would be another gravitational
force which would act between the
satellite and the earth so that will be
given by G into M that is mass of the
satellite Capital m V that is mass of
the earth divided by r e + H whole
square now this is the force which will
balance the centripetal force F C so
therefore these two forces should be
equal that is FC should be equal to F G
now let us equate both the forces so it
will become MD
square divided by re plus h is equal to
G M mg divided by R + H whole square
right so this RT plus h and this re + H
will get cancelled this m and this M
will also get cancelled so we get V
square is equal to g m-e / r e plus h so
we get from this p is equal to root over
2 root over g m-e divided by r e plus h
so this would be the velocity with which
the satellite would be revolving around
the earth so this would be the velocity
now we want to calculate the time period
right so we will do that now we know
that the satellite would cover 2 pi r e
plus h that is the circumference right 2
pi r t + H distance with speed V with
speed V which we calculated just now
therefore the time period would be equal
to 2 pi r e + h that is the total
distance traveled divided by the
velocity v so this will be equal to 2 pi
r e + h divided by root over g m-e into
root over r-e + h i have just put the
value of v from the previous equation
which we got in the previous slide
therefore value of t comes out to be 2
pi r e plus h to the power 3 by 2
divided by root over g m-e so this is
nothing but the time period of our
satellite which revolves around the
ugh so this is how we calculate the
velocity of a satellite with which it
revolves around the earth as well as the
time period of the satellite with which
it orbits around the earth now we will
also consider a special case of this so
we will see a special case a special
case when H that is the height which we
consider it like if suppose this is the
earth and this is your satellite so this
is radius of the earth and this
distances H if we say that H is very
very less than R T what will happen in
that case in that case R a plus h can be
approximated to R T because H is very
small when compared to a T so T will be
equal to 2 pie root over r-e cube
divided by g m-e now this we can write
in terms of acceleration due to gravity
as root over r-e divided by G because G
is equal to g m-e by are in spread so
using that we can write this so this
will become the time period in case of
in case H is very very less than Rd that
means if the satellite is very close to
the surface of the earth so in that case
we will arrive at this solution so you
saw how do we calculate the time period
for a satellite as well as the velocity
with which the satellite moves around
the planet now we will go ahead and we
will see the energy of an orbiting
satellite now we will find out an
expression to evaluate the energy of an
orbiting satellite before this we saw
how to calculate the time period and
velocity of a satellite which is
orbiting around the earth now we will
see how do we evaluate the energy of an
orbiting satellite now let us suppose
that for the
at late we consider that M is the mass
of the satellite and the velocity with
which it is moving around the earth is V
so M is mass velocity is V so what would
be the kinetic energy of the satellite
it would be half M field square now we
have already found out the value of V
just in the previous topic so V is
nothing but g m-e divided by r e plus h
so we get the kinetic energy as half m g
m e / r e plus h now let us calculate
the potential energy so what would be
the potential energy it would be minus g
m-e into m / r e plus h now if you see
the values of kinetic energy and
potential energy you can find out the
total value of energy that is total
energy is nothing but kinetic energy
plus potential energy so if you
calculate that it is half m g into m e /
r e + h + - g m-e so + - would be - so -
g m-e into m / r e plus h so this comes
out to be minus g m-e into m / r e + h
so this is the value of total energy
right so what do we observe from this we
observe the conclusion first conclusion
is we find we found that potential
energy is equal to so we found that
potential energy is equal to twice the
value of kinetic energy if you see the
value of potential energy you can very
clearly see that half of potential
energy is kinetic energy right and what
is the second conclusion the total
energy is negative that means so that
meant when the total energy is negative
that means this is
is a bound system that means the system
cannot escape so this shows that this is
our earth later suppose and this is the
satellite since the total energy is
negative therefore the satellite is
bound to this earth satellite system and
it is moving in this fashion otherwise
it would have just escaped from the
attraction pool of the earth and it
would have not moved in and particular
orbit so this also indicates from the
fact that total energy has a negative
sign now we'll go ahead and look at
certain problems regarding all the
topics which we have studied so far
thank you please visit exam vo comm to
watch free educational videos try free
online tests get the best quality study
materials study from the best tutors and
mentors and much more thank you once
again
About this Video
Oct 22, 2025
Last updated
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