B What happen if i put r=0 into the formula F=(k)mm/r^2

[garylau]

What happen if i put r=0 into the formula F=(k)mm/r^2
So 1/0=infinity ?

then F= infinite large in mathematical sense?
is that statement correct ?

thank

 

[BvU]

That's what happens with the formula. In reality you can't have two masses in exactly one place, so the formula isn't endlessly applicable...

Mathematically you have a singularity.

 

[garylau]

That's what happens with the formula. In reality you can't have two masses in exactly one place, so the formula isn't endlessly applicable...

Mathematically you have a singularity.

But In reality i can have two mass put in r=0.000001m
So the force still become very large?

 

[member 587159]

What happen if i put r=0 into the formula F=(k)mm/r^2then F= infinite large in mathematical sense?
is that statement correct to say F is infinitely large?

You cannot put in r = 0. That does not make sense. It does make sense to consider:

$\lim_{r \to 0}F = +\infty$. This means, intuitively, when $r$ approaches $0$, $F$ becomes larger and larger (F grows without bound).

 

[BvU]

But In reality i can have two mass put in r=0.000001m
So the force still become very large?

Well, the masses become smaller too for such small particles. One micron diameter with a reasonable density gives a very small mass !

On even smaller scales still other things happen. Protons, for example have a mass of only 1.67 10^-31 kg and a diameter of 0.88 10^-15 m. At such small scales other kinds of forces are much stronger.

 

[garylau]

Well, the masses become smaller too for such small particles. One micron diameter with a reasonable density gives a very small mass !

On even smaller scales still other things happen. Protons, for example have a mass of only 1.67 10^-31 kg and a diameter of 0.88 10^-15 m. At such small scales other kinds of forces are much stronger.

is it possible that the mass is very large but the r is very small?

 

[Demystifier]

is it possible that the mass is very large but the r is very small?

Yes. Moreover, in quantum physics mass is, in a certain sense, proportional to $1/r$.

 

[mfb]

is it possible that the mass is very large but the r is very small?

Yes, then you get a very large force. But it is always finite. And if you want to put the masses too close, you have to consider quantum mechanics where the simple approach with a well-defined distance fails.