Q. If the sun were suddenly replaced by a block hole of one solar mass, what would happen to the earth's orbit immediately after the replacement ?

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The earth would spiral into the black hole

The radius of the earth's orbit would be unchanged, but the period of the earth's motion would increase

The radius of the earth's orbit would be unchanged, but the period of the earth's motion would decrease

Neither the radius of the orbit nor the period would change

Solution:

As the mass of earth remain same, nothing would happen because all gravitational forces remain same.

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