A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98 1024 kg) have to be compressed to be a black hole?
- 10-9 m
- 10-6 m
- 10-2 m
- 100 m
Answer
(3) 10-2 m
Solution
For a black hole, escape speed c: 2GMR = c
R = 2GMc2
= 2 6.67 10-11 5.98 1024(3 108)2
8.9 10-3 m 10-2 m
Answer: (3)