# Force of magnets

1. Oct 26, 2005

### aneima6

Magnet A has twice the magnetic field strength of magnet B (at equal distance) at a certain distance and pulls on the magnet B with a force of 30N. Determine the force with which magnet B pulls magnet A.
Could someone help me. I'm just starting physics in hs.

Last edited: Oct 26, 2005
2. Oct 26, 2005

### Tide

Do you have any reason to believe the forces will be different - i.e. Newton's law of action reaction does not apply?

3. Oct 26, 2005

### aneima6

thats probably correct. this is a basic question. i think it is getting at coulombs law.

i think the answer is 15N. not sure

4. Oct 26, 2005

### Tide

If you're talking about magnets you're probably not dealing with Coulomb's law.

So, why do you think the answer is 15 N?

5. Oct 26, 2005

### aneima6

well i'm not exactly sure. i'm looking in the chapter of magnetism in my book and i don't see any forumla's. its weird. i went back a chapter and found coulombs which deals with force=(k)(q1q2)/d^2.

i wasn't sure if it was right or now. if you could help me on a formula i could try and solve it. thanks

jeff

6. Oct 26, 2005

### aneima6

i think because magnet a is twice as strong, that magnet b is half of its strength.

also i forgot a few parts of the question that might help

it has twice the magnetic field strength.

Last edited: Oct 26, 2005
7. Oct 26, 2005

### Tide

I have no idea what equations your textbook shows but if you have none relating the pulling force of a magnet that should be a clue for you!

Remember Newton's Law that I mentioned earlier and think about this: If a magnet is twice as strong then not only it will it pull another with twice the force it will also be pulled with twice the force!

8. Oct 26, 2005

### aneima6

so the answer is that since they are an equal distance away. that the force that a acts upon b is the same force that b acts upon a.