# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Edwina Lee on 20/08/2020 10:59:51

Title: Which forces are directable
Post by: Edwina Lee on 20/08/2020 10:59:51
Which force fields are directable so that it is possible to affect an object from a distance?
Title: Re: Which forces are directable
Post by: alancalverd on 20/08/2020 14:13:55
Electric and magnetic fields propagate through space but are difficult to direct over distances greater than the diameter of the source.

Magnetic fields need a return path that doesn't upset other people's computers, but do have the ability to suck some objects.

Gravity sucks radially and not very well.

Electromagnetic radiation of lower frequency than x-rays can be focussed or, particularly in the case of laser radiation, propagated as a parallel beam.

You can transmit a lot of momentum in a bullet.

Wherever I have to move an object at a distance, my first preference is to use a stick or a string.
Title: Which forces are directable
Post by: CharlesCably on 25/08/2020 06:36:01
The first question to answer is: which system object are you studying? The spring? The mass is it supposed to be the representation of the line?

Then you can start illustrating the forces applied to the object and apply Newtons law

Merlin
Title: Re: Which forces are directable
Post by: evan_au on 25/08/2020 09:58:34
Quote from: OP
possible to affect an object from a distance?
The Strong and Weak Nuclear forces work over a distance - but it is an extremely small distance.

The Strong force manages to almost hold together a Uranium nucleus.
The Weak force has a much shorter range.

https://en.wikipedia.org/wiki/Nuclear_force
Title: Re: Which forces are directable
Post by: Edwina Lee on 25/08/2020 12:53:39
'm most interested in directing objects on earth & in space.
As AlanCaverd said "Electric and magnetic fields propagate through space but are difficult to direct over distances greater than the diameter of the source.", then it should be possible to use magnetic ring(s) of about 15 mile diameter to lift weights from the ground into space.
What formulae ?

Title: Re: Which forces are directable
Post by: Bored chemist on 25/08/2020 13:04:28
What formulae ?
With conventional rockets this formula is fairly close to right
Price of putting something in space = weight in gold.

Using magnets wouldn't be any cheaper- or they would have done it.
Title: Re: Which forces are directable
Post by: alancalverd on 25/08/2020 15:29:17
it should be possible to use magnetic ring(s) of about 15 mile diameter to lift weights from the ground into space.
Quite possibly, but at the expense of pulling the nails out of church doors and making aeroplanes fly in circles.

Electromagnetic rail guns have been suggested  as a first-stage launcher.