## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

We can use the equation for escape speed to find the radius $R$ of the event horizon. $v = \sqrt{\frac{2~G~M}{R}}$ $v^2 = \frac{2~G~M}{R}$ $R = \frac{2~G~M}{v^2}$ $R = \frac{(2)(6.67\times 10^{-11}~m^3/kg~s^2)(5.0)(1.99\times 10^{30}~kg)}{(3.00\times 10^8~m/s)^2}$ $R = 1.47\times 10^4~m$ $R = 14.7~km$ The radius of the event horizon is 14.7 km