Tag: moon and stars in sky

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Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

The distance of the moon from the earth is about 60 times the radius of the earth. What will be diameter of the earth (approximately in degrees) as seen from the moon.?

  1. $1^o$.

  2. $2^o$.

  3. $4^o$.

  4. $6^o$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

From figure
We know the formula 

$\theta=\dfrac{Diameter \ of \ earth}{R}$

$\displaystyle \theta = \frac{2R _E}{60 R _E}$

$= \dfrac{1}{30} rad = \dfrac{1}{30} \times \dfrac{180^o}{\pi} = 2^o$

The diameter of the earth as seen from the moon is about $2^o$.
Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

Which one of the following statements is correct?

  1. The energy required to rocket an orbiting satellite out of earth's gravitational influence is more than the energy required to project a stationary object at the same height (as the satellite) out of earth's influence.

  2. If the zero of potential energy is at infinity, the total energy of an orbiting satellite is negative of potential energy.

  3. The first artificial satellite Sputnik I was launched in the year 1950.

  4. The orbital speed of the SYNCOMS (synchronous communications satellite) is $3.07\times10^{2}m s^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The energy required to rocket an orbiting satellite out of earth's gravitational influence is less than the energy required to project a stationary object at the same height (as the satellite) out of earth's influence.
Hence, option (a) is incorrect statement.


If zero of potential energy is at infinity, the total energy of an orbiting satellite is negative of its kinetic energy.
Hence, option (b) is an incorrect statement.

The first artificial satellite was launched by Soviet scientists in the year 1957.
Hence, option (c) is an incorrect statement.

The orbital speed of the SYNCOMS is $v=\dfrac{2\pi{r}}{T}=\dfrac{2\times3.14\times4.22\times10^{7}}{8.64\times10^{5}}$
$=3.07\times10^{2}m s^{-1}$
Hence, option (d) is a correct statement.

Multiple choice evs search of life outside earth types of artificial satellites geostationary orbits moon and stars in sky

Out of the following, the only correct statement about satellites is

  1. A satellite cannot move in a stable orbit in a plane passing through the earth's centre

  2. Geostationary satellites are launched in the equatorial plane

  3. Satellites are rectangular in shape. 

  4. Geostationary satellites are launched in axial plane
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Geostationary satellites are launched to the equitorial plane, so the it could have a time period of 24 hours exact and can have maximum reach, i.e on both heminpheres for information transfer.

Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

State whether the given statement is True or False :

It is possible to put an artificial satellite into orbit in such a way that it will always remain directly over New Delhi.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Geostationary satellite appears to be stationary above particular point on the Earth. We can have geostationary satellites only above equator. If it is not above the equator then it will change its position relative to particular position of the Earth which we do not want. 

Since New Delhi is not on the equatorial plane and geostationary satellite is launched on the equatorial plane, so the satellite will not remain directly over New Delhi. 
Therefor, the given statement is false.

Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

A satellite is orbiting around the earth in an orbit in equatorial plane, of radius 2$R _{e}$ , where $R _{e}$ is theradius of the earth. Find the area on the earth, this satellite covers for communication purpose in its complete revolution 

  1. $4\pi R _{e}^{2}$

  2. $2\pi\sqrt{3} R _{e}^{2}$

  3. $2\pi(2-\sqrt{3}) R _{e}^{2}$

  4. $2\pi(4+\sqrt{3}) R _{e}^{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

Two satellites A & B go around the earth in a circular orbits at a heigh of $R _{A} & R _{B}$ respectively from surface of the earth. Assume earth to be a uniform sphere of radius $R _{e}$ The ratio of the magnitudes of velocities of the satellite $V _{A}/V _{B}$ is

  1. $\sqrt{\frac{R _{A}}{R _{B}}}$

  2. $\left ( R _{A}/R _{B} \right )^{2}$

  3. $\frac{R _{B}+R _{e}}{R _{A}+R _{e}}$

  4. $\sqrt{\frac{R _{B}+R _{e}}{R _{A}+R _{e}}}$
Reveal answer Fill a bubble to check yourself
A Correct answer