<p>Aside from gravity, electromagnetic forces can change the momentum of a charged black hole. </p>

<p>When something falls into a BH momentum is conserved according to every observer, although they may have very different ideas of how that happens. A distant observer will see the new black hole as having some momentum and so moving in some direction relative to the trajectory of the old black hole. It's not really appropriate to describe it as pushing, though. From the object's perspective, nothing special happens as it passes the event horizon. From a distant observers perspective, the gravitational field of the moving object merges with that of the black hole, and the result is the field of a slightly bigger and slightly moving black hole.</p>

CC BY-SA 4.0
2019-10-05T00:23:57.120Z
I was thinking of this in terms of equal and opposite reactions but was not sure how the surface of the black hole responded to force since the object passes the event horizon which appears to be the surface.
Max Young
CC BY-SA 4.0
2019-10-03T22:57:28.137Z
2019-10-03T22:57:28.137Z
Steve Linton
<p>Besides gravity I have never heard of another force pushing or pulling a black hole. Does an object falling into a black hole push the black hole when it crosses the event horizon? What happens to the kinetic energy of an object that enters a black hole?</p>

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2019-10-03T17:20:55.413Z
Forces act on all masses the same regardless of density.  Can you explain in more detail what exactly you might expect to be different in this case?
Carl Witthoft
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2019-10-04T01:42:55.033Z
I think black holes can have charge, but don't know for sure. It would be pretty hard to make it very large though.
uhoh
CC BY-SA 4.0
2019-10-05T00:21:18.483Z
@CarlWitthoft I wasn't really sure that the object would ever impact the surface of the black hole. Is the event horizon some that can have force applied to it?
Max Young
<black-hole>
In what ways can force be applied to a black hole
Max Young
# In what ways can force be applied to a black hole

(Asked by: username_0 on 2019-10-03)

Besides gravity I have never heard of another force pushing or pulling a black hole. Does an object falling into a black hole push the black hole when it crosses the event horizon? What happens to the kinetic energy of an object that enters a black hole?

**Tags:** black-hole
> **Comments:**
> **username_1**: Forces act on all masses the same regardless of density.  Can you explain in more detail what exactly you might expect to be different in this case?  
> **username_2**: I think black holes can have charge, but don't know for sure. It would be pretty hard to make it very large though.  
> **username_0**: @CarlWitthoft I wasn't really sure that the object would ever impact the surface of the black hole. Is the event horizon some that can have force applied to it?  

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## 1 answers

### Answer by username_3 on 2019-10-03. Score: 4 | Accepted answer

Aside from gravity, electromagnetic forces can change the momentum of a charged black hole.

When something falls into a BH momentum is conserved according to every observer, although they may have very different ideas of how that happens. A distant observer will see the new black hole as having some momentum and so moving in some direction relative to the trajectory of the old black hole. It's not really appropriate to describe it as pushing, though. From the object's perspective, nothing special happens as it passes the event horizon. From a distant observers perspective, the gravitational field of the moving object merges with that of the black hole, and the result is the field of a slightly bigger and slightly moving black hole.

> **Comments:**
> **username_0**: I was thinking of this in terms of equal and opposite reactions but was not sure how the surface of the black hole responded to force since the object passes the event horizon which appears to be the surface.  

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