Randall D. Knight — Newton's Theory of Gravity: Problem 21

Nothing can escape the event horizon of a black hole, not even light. You can think of the event horizon as being the distance from a black hole at which the escape speed is the speed of light, \(3.00 \times 10^8 \text{ m/s}\), making all escape impossible. What is the radius of the event horizon for a black hole with a mass 5.0 times the mass of the sun? This distance is called the Schwarzschild radius.