Astronomy
Black Holes
Astrophysics

# How much gravity does a black hole have?

###### 03/05/2013

The gravitational force that a black hole has on another object depends on the following:

1. The mass of the black hole

2. The mass of the object

3. The distance between the centres of the black hole and the object (r)

Using Newton's Law of Universal Gravitation, this force can be calculated using the following equation:

F=G*[(m1*m2)/(r2)]

where:

F = force

G = universal gravitational constant = 6.674

###### 03/05/2013

The gravitational force that a black hole has on another object depends on the following:

1. The mass of the black hole

2. The mass of the object

3. The distance between the centres of the black hole and the object (r)

Using Newton's Law of Universal Gravitation, this force can be calculated using the following equation:

F=G*[(m1*m2)/(r2)]

where:

F = force

G = universal gravitational constant = 6.674Ã—10âˆ’11 N m2 kgâˆ’2

m1 = mass of the first object

m2 = mass of the second object

r = distance between the centres of the objects

If, however, you wish to calculate the surface gravity of a black hole - which refers to the gravitational acceleration that's experienced at its surface (i.e. the event horizon) - then a different equation is used:

k = c4/[4Gm]

Where:

k = surface gravity

c = speed of light in a vacuum = 3x108m/s

G = universal gravitational constant = 6.674Ã—10âˆ’11 N m2 kgâˆ’2

m = mass of the black hole