# The gravitational radius of a black hole is visible from its satellite at an angle of 1 “.

September 15, 2020 | Education

| **The gravitational radius of a black hole is visible from its satellite at an angle of 1 “. Determine the linear velocity of the satellite’s circular revolution.**

Since the gravitational radius is visible at an angle of 1 ‘or (1/3400) radians, the satellite orbits with a radius of 3400 gravitational radii. At this distance, we can use the formulas of classical celestial mechanics. The second cosmic velocity is (2GM / r) ^ 1/2, that is, it decreases in inverse proportion to r ^ 1/2. At a given distance, it will be (3400) ^ 1/2 ~ 58 times less than the speed of light and will be 5100 km / s. The first cosmic (circular) speed will be 2 ^ 1/2 times less and will amount to 3600 km / s.

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