Problem 71-7
Source: Entrance Exam FUVEST - SP - 2019.
Two identical spherical metallic objects, containing electrical charges of 1 C and 5 C,
are placed in contact and then spaced at a distance of 3 m. Considering the Coulomb constant
K = 9 x 109 N m2/C2, calculate the force acting between the charges
after contact and whether it is of attraction or repulsion.
Solution of the Problema 71-7
When we put the two identical spheres in contact, there will be a redistribution of the charges.
They will stay symmetrically distributed and each sphere will have a charge of 3 C each
(the arithmetic mean between them or (1 + 5) / 2 = 3 C ). So, by separating one from
another for a distance of 3 meters , there will be a force of repulsion between
them of modulus equal to
Performing the calculation we find the magnitude of the repulsion force, or
