Geography · Physics

Geodesy and Celestial Mechanics

1,049 Questions

Geodesy and celestial mechanics questions explore Earth measurements, great circles, and planetary motions. These concepts form a crucial part of physical geography and astronomy in competitive exams. Practice these questions to grasp longitudinal and latitudinal calculations.

Longitude and latitude calculationsGreat circle conceptEarths axial precessionLagrangian pointsAtmosphere boundary

Geodesy and Celestial Mechanics Questions

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

What is the approximation made in the parallax method?

  1. All distances measured between two points on earth is zero.

  2. All distances measured between two points on earth is constant.

  3. Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth's surface.

  4. No approximation is made.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In parallax method, an approximation is made that distance between a point on the earth and the planet is very large as compared to the distance between two points on the earth's surface.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

Parallax angles _______ $0.01/ arcsec$ are very difficult to measure from Earth.

  1. more than

  2. less than

  3. equal to

  4. greater than or equal to
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Parallax effect depends upon the path of light that travels from object to the observer. For distant objects observed from Earth, the light that reaches Earth has to go through a number of layers in Earth's atmosphere, during which it refracts and disperses and hence decreases the accuracy of the method. Resultantly parallax angles less than $0.01/arcsec$ are very difficult to measure from Earth.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

A star is $1.45\ parsec$ light years away. How much parallax would this star show when viewed from two locations of the earth six months apart in its orbit around the sun?

  1. $2\ Parsec$
  2. $0.725\ Parsec$
  3. $1.45\ Parsec$
  4. $2.9\ Parsec$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

One light year $=$ speed of light $\times$ one year

or $1 ly=3\times 10^8\times (24\times 3600)=94608\times 10^{11} m$
So, $4.29 ly=4.29\times (94608\times 10^{11})=4.058\times 10^{16} m$
As $1 $ parsec $=3.08\times 10^{16} m$
(Parsec is a unit of length used to measure large distances to objects outside our Solar System)
Thus, $4.29 ly=\dfrac{4.058\times 10^{16}}{3.08\times 10^{16}}=1.32$ parsec
Now angular displacement , $\theta=\dfrac{d}{D}$
where $d=$ diameter of earth's orbit $= 3\times 10^{11} m$ and 
$D=$ distance of star from the earth $=4.058\times 10^{16} m$
So, $\theta=\dfrac{3\times 10^{11}}{4.058\times 10^{16}}=7.39\times 10^{-6}$ rad
As $1 sec=4.85\times 10^{-6} rad$ so, $7.39\times 10^{-6} rad=\dfrac{7.39\times 10^{-6}}{4.85\times 10^{-6}}=1.52 sec$

Multiple choice magnetic compass magnetic poles and magnetic compass properties of magnet effect of electric current physics

The marked end of a compass needle always points directly to

  1. Earth's geographic South Pole

  2. Earth's geographic North Pole

  3. A magnet's south pole

  4. A magnet's north pole
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The marked end of compass needle always points to the south pole of a magnet.

The geographic north pole of the earth is the magnetic south pole. 
Hence it points towards the geographic north pole of earth.

Multiple choice magnetic compass magnetic poles and magnetic compass properties of magnet effect of electric current physics

At a certain location in Africa, compass points $12^0$ west of geographic north. The north tip of magnetic needle of a dip circle placed in the plane of magnetic meridian points $60^0$ above the horizontal. The horizontal component of earth's field is measured to be $0.16$G. The magnitude of earth's field at the location is :

  1. $0.32$G
  2. $0.42$G
  3. $4.2$G
  4. $3.2$G
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Here, $H _E = 0.16G = 0.16 \times 10^{-4}T$, dip angle $(\delta) = 60^0$
Then, magnitude of earth's field.
$B _E = \dfrac{H _E}{cos \delta} = \dfrac{0.16 \times 10^{-4}}{cos 60^0} T \Rightarrow B _E = \dfrac{0.16 \times 10^{-4}}{1/2} = 0.32 \times 10^{-4}T = 0.32G$

Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

The magnetic south pole of the earth is situated near the 

  1. geographic south pole

  2. geographic north pole

  3. geographic east

  4. geographic west
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

'Magnetic North' is a LOCATION, so-named to distinguish it from True North -it has NOTHING to do with its magnetic POLARITY. The magnetic polarity at this location is south -which is why it attracts the north-seeking pole of a compass needle or magnet.

Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

The angle of declination at a place is the angle

  1. Between the vertical plane and the geographical meridian

  2. Between the vertical plane and the magnetic meridian

  3. Between the geographical meridian and magnetic meridian

  4. Between the geographical meridian and horizontal plane
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A freely suspended magnet always points in the North-South direction even in the absence of any other magnet. This suggests that the Earth itself behaves as a magnet which causes a freely suspended magnet (or magnetic needle) to point always in a particular direction: North and South.

The vertical plane passing through the axis of a freely suspended magnet is called magnetic meridian. The direction of Earth's magnetic field lies in the magnetic meridian and may not be horizontal. The vertical plane passing through the true geographical North and South (or geographical axis of Earth) is called geographical meridian. The angle between the magnetic meridian and the geographic meridian at a place is called declination at that place.

Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

The bulging of earth at the equator and flattening at the poles is due to 

  1. Centripetal force

  2. Centrifugal force

  3. Gravitational force

  4. Electrostatic force
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The bulging of equator and flattening at poles is due to rotation of earth. The rotation of earth creates a centrifugal force which is pseudo effect counter balancing the inward acting centripetal force. This pseudo effect pushes the earth outward, bugling from earth, and flattening at poles. 

Hence correct answer is option B.

Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

Define angle of declination at a place :

  1. angle between the vertical plane and the geographical meridian

  2. angle between the vertical plane and the magnetic meridian

  3. angle between the geographical meridian and the magnetic meridian

  4. angle between the geographical meridian and horizontal plane
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the magnetic force lines along the surface of the earth. Therefore a compass needle will be parallel to the magnetic meridian.

The angle between the magnetic and the true meridian is the angle of declination, which is relevant for navigating with a compass.

Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

The north pole of earth's magnet is near __________.

  1. geographic north

  2. the centre of earth

  3. geographic south

  4. Both (A) and (C)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The opposite poles of two magnets attract.
So, north pole of earth's magnet is near the geographic south. The magnetic field created by the molten core of the earth have a magnetic south pole near the geographic north pole to attract N-pole.
Hence, option : C.
Multiple choice physics properties of a magnetic field earth - a gigantic magnet magnetic field of earth introduction to magnetic field and magnetic flux

The actual north magnetic pole of earth

  1. Is situated near the geographic south pole.

  2. Is north pole of the magnetic substance of the earth's core.
  3. Attracts the $N$ pole of the compass needle.
  4. Both $(1)$ and $(2)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reason for the magnetic field of the earth is the magnetic substance in the earth’s core. 

So the pole of the earth is the pole of the magnetic substance in the earth’s core.

The actual north magnetic pole of earth is situated near the geographic south pole because the unlike poles attract each other.