Q.

Assume that the earth is a solid sphere of uniform density and a tunnel is dug along its diameter throughout the earth. It is found that when a particle is released in this tunnel, it executes a simple harmonic motion. The mass of the particle is 100 g. The time period of the motion of the particle will be (approximately)

(take g = 10 ms-2, radius of earth = 6400 km)                    [2023]

1 1 hour 24 minutes  
2 1 hour 40 minutes  
3 12 hours  
4 24 hours  

Ans.

(1)

T=2πRg=2π6400×10310

=2π×8×102=16π×102=5024 s=83.73 min

=1 hr 23.73 min

1 hr 24 min