Question Details

One project after deviation from its path, starts moving round the earth in a circular path at radius equal to nine times the radius at earth R, its time period will be

Options

A

2π √(R/g)

B

27 x 2 π √(R/g)

C

π √(R/g)

D

8 x 2π √(R/g)

Correct Answer :

27 x 2 π √(R/g)

Solution :

The correct option is 27 x 2 π √(R/g).

To find the time period of the object moving in a circular orbit around the Earth, we can analyze the orbital mechanics from first principles.

For a circular orbit of radius r around the Earth, the gravitational force acting on the object of mass m provides the necessary centripetal force:
GMmr2=mv2r
where G is the universal gravitational constant, M is the mass of the Earth, and v is the orbital velocity of the object.

Solving for the orbital velocity v gives:
v=GMr

The orbital period T is the time taken to complete one full revolution of circumference 2πr:
T=2πrv=2πr3GM

We can relate the term GM to the acceleration due to gravity g at the Earth's surface (radius R):
g=GMR2GM=gR2

Substituting GM=gR2 back into the time period equation gives:
T=2πr3gR2

The problem states that the radius of the circular path is equal to nine times the radius of the Earth, so we substitute r=9R:
T=2π(9R)3gR2

Simplifying the mathematical expression:
T=2π729R3gR2
T=2π729Rg

Since 729=27, we obtain:
T=27×2πRg

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