## anonymous one year ago help! :)

1. anonymous

@Michele_Laino

2. anonymous

@calculusxy

3. geerky42

With what?

4. anonymous

can you explain what opposites are and give examples of real world situations? :)

5. anonymous

@Michele_Laino just explain it in your own words :)

6. Michele_Laino

for example -5 and +5 are opposite with respect to addition, since we have: -5+(+5)=0, and 0 is the neutral element of addition of the set of integers

7. anonymous

ok thats the example?

8. Michele_Laino

yes it is an example which comes from mathematics

9. anonymous

ok and can you explain what opposites are

10. Michele_Laino

here is another example from physics: north pole and south pole are opposite, since between them there is an attractive force

11. Michele_Laino

I meant norh pole and south pole of a magnet

12. anonymous

ok i get the examples, but can you explain what opposites are not in an example please :)

13. Michele_Laino

referring to the quantum electrodynamics processes, I can say that opposites element are such that when they are both presents, they disappear and a new form of energy will appears

14. Michele_Laino

such process is called annihilation

15. anonymous

ok next question! :)

16. anonymous

can you describe multiplying and dividing signed numbers in the real world?

17. Michele_Laino

yes, I know an example from physics, nevertheless it is difficult to understand.

18. anonymous

19. Michele_Laino

it is related to a solid state physics of semiconductors. When we study semiconductors, we have to introduce the so called effective mass of a carrier of electricity, and such effective mass is negative. Of course such effective mass can be multiplied for a positive quantity in order to get another quantity

20. Michele_Laino

another simpler example comes from the Coulomb law, which is related to the interaction between a positive charge and a negative charge, for example. So in order to get the magnitude of the interaction force between a positive and a negative electric charges, I have to multiply a negative quantity with a positive quantity, using the subsequent algebrauc expression: $\Large F = K\frac{{{Q_1}{Q_2}}}{{{r^2}}}$ where Q1>0, Q2<0, r>0 and K>0

21. anonymous

this is all so confusing!