Thank you for your help,
in brief, i only found the vector on the x-axis (cuz as you said the y-component should be canceled) and replaced the sin by tan (because of the very long distance of the y-component of the proton, which was nearly equal to the distance between the proton and one of...
Hi,
I had this question in my homework:
An electric dipole consists of two equal loads and signs opposite separated by one distance which equals 2a. Show how the module of the electric force resulting on a proton (load +e) placed directly on the Y=axis at a very long distance from the dipole...