A small m=2.00-g plastic ball is suspended by a L=20.0-cm-long string in a uniform electric field E, as shown in Figure. If the ball is in equilibrium when the string makes a theta=15.0° angle with the vertical as indicated, what is the net charge on the ball?
Sulla pallina agiscono peso P, tensione fune T e forza elettrica F
La pallina è ferma:
orizzontale. F=qE=T sin theta
verticale. P=mg = T cos theta
q= ( mg tg theta) / E