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Earth may be assumed to be an axially symmetric freely rotating rigid body. The ratio of the principal moments of inertia about the axis of symmetry a
Question

Earth may be assumed to be an axially symmetric freely rotating rigid body. The ratio of the principal moments of inertia about the axis of symmetry and an axis perpendicular to it is 33:32. If T is the time taken by earth to make one rotation around its axis of symmetry, then the time period of precession is closest to

A.

33 T₀

B.

33 T₀ /2

C.

32 T₀

D.

16 T₀

Correct option is C

Given:
1. Earth is an axially symmetric, freely rotating rigid body.
2. The ratio of the principal moments of inertia about the axis of symmetry Iz I_z ​ and an axis perpendicular to it Ix=IyI_x = I_y ​ is given as Iz:Ix=33:32I_z : I_x = 33 : 32​ .
3.  T0 is the time taken by Earth to make one rotation around its axis of symmetry.
The time period of precession  T  of a symmetric rigid body is given by:
T=2πIx(IzIx)ω\\ T = \frac{2 \pi I_x}{(I_z - I_x) \omega} \\​​
where:
Ix  is the moment of inertia about an axis perpendicular to the axis of symmetry.
 Iz  is the moment of inertia about the axis of symmetry.
 ω  \ \omega \ ​is the angular velocity of Earth's rotation around its axis of symmetry.
Solution:
Expressing Moments of Inertia Using the Given Ratio:
- We are given  Iz:Ix=33:32\ I_z : I_x = 33 : 32 ​​
Let Ix=32k and Iz=33k for some constant k.\text{Let } I_x = 32k \text{ and } I_z = 33k \text{ for some constant } k.

2. Calculate IzIx:\text{2. Calculate } I_z - I_x:

IzIx=33k32k=kI_z - I_x = 33k - 32k = k

3. Angular Velocity ω:\text{3. Angular Velocity } \omega: - The angular velocity ω of Earth’s rotation is related to the rotation period T0 by:\text{- The angular velocity } \omega \text{ of Earth's rotation is related to the rotation period } T_0 \text{ by:} ω=2πT0\omega = \frac{2 \pi}{T_0}

4. Substitute into the Precession Period Formula:\text{4. Substitute into the Precession Period Formula:} Substitute Ix=32k, IzIx=k, and ω=2πT0 into the formula:\text{Substitute } I_x = 32k, \, I_z - I_x = k, \text{ and } \omega = \frac{2 \pi}{T_0} \text{ into the formula:} T=2π32kk2πT0T = \frac{2 \pi \cdot 32k}{k \cdot \frac{2 \pi}{T_0}}

T=2π32kT0k2π=32T0T = \frac{2 \pi \cdot 32k \cdot T_0}{k \cdot 2 \pi} = 32 T_0

Final Answer:\text{Final Answer:} The time period of precession is closest to: 32 T0\text{The time period of precession is closest to: } 32 \, T_0​​​​

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