# Vectorial description of two forces

1. Apr 27, 2009

### Plott029

I need to know if it's posible that this two vectors could be the same:

$$\vec f_1_2 = \vec v_1_2 [ \frac {\partial q_1_2 \vec E_1_2} {\partial t} + \nabla( \vec E_1_2 \vec v_1_2 ) ]+ q \vec E_1_2 [ \frac {\partial \vec v_1_2} {\partial t} + ( \vec {v_1_2} \nabla ) \vec v_1_2 ]$$

$$\vec f_2_1 = \vec v_2_1 [ \frac {\partial q_2_1 \vec E_2_1} {\partial t} + \nabla( \vec E_2_1 \vec v_2_1 ) ]+ q \vec E_2_1 [ \frac {\partial \vec v_2_1} {\partial t} + ( \vec {v_2_1} \nabla ) \vec v_2_1 ]$$

How must I start to know how to "force" the conditions to make the two vectors, equal?