Question

Doua bile metalice,identice,incarcate cu aarcini electrice de acelasi semn q si 4q se afla la dustanta r . Se aduc bilele in contact si apoi se indeparteaza la distanta x, astfel incat forta de interactiune sa ramana aceeasi. Sa se determine x. R:x=1,25r

Answer 1

Initial :

F=4q^2k/r^2

Cand bilele se ating sarcina lor devine

q1=q2=(4q+q)/2=2,5q

In final

F=6,25q^2k/x^2

4q^2k/r^2=6,25q^2k/x^2

4/r^2=6,25/x^2
4x^2=6,25r^2
2x=2,5r
x=2,5r/2
x=1,25r