Problem 71-2
Source: Problem developed by the author of the site.
We see in Figure 71-02.1 the distribution of three particles, Q1, Q2
e Q3, in the x-y plane. If the three particles
have the same charge, being equal to + 5 µC, calculate the force, in module and direction,
that the particle Q3 suffers in the presence of the other two.
What happens to two electrical charges, +Q y -q placed at a distance d
between each other, if we change the charge + Q by +4 Q, the charge
-q by +3 q and the distance d by 2 d?
The scheme presented in Figure 71-05.1 represents the metallic spheres A and B,
both with mass of 10-3 Kg and electrical charge of module equal to 10-6 C.
The spheres are attached by insulating wires to supports, and the distance between them is 1 meter .
Assume that the wire holding the sphere A has been cut and that the resulting force on that sphere
corresponds only to the force of electrical interaction. Calculate the acceleration, in m/s, acquired
the sphere A immediately after cutting the wire.
Problem 71-6
Source: Entrance Exam FUVEST - SP - 2019.
Three small spheres charged with positive charge, Q, occupy the vertices of a triangle,
as shown in Figure 71-06.1. Inside the triangle, another small sphere is affixed,
with negative charge, -q. The distances of this charge to the other three can be obtained from
the figure.
Calculate the resulting electrical force (in module, direction and direction) on the charge q,
knowing that:
Q = 2 x 10-4 C,
q = - 2 x 10-5 C, x = 6 m, and
K = 9 x 109 N m2/C2
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.
Problem 71-8
Source: Adapted of the Problem 76 - page 817 - KNIGHT, Randall D. -
Book:
Física - Uma Abordagem Estratégica - 2ª Edição - Ed. Bookman - 2009.
In Figure 71-08.1 a force F = 1.94 x 10 -4N, represented on the charge of
- 1 nC.
Determine the nature of the charge q and its value, as well as the value of the force
attraction or repulsion on the negative charge.
Problem 71-9
Source: Problem 75 - page 817 - KNIGHT, Randall D. - Book:
Física - Uma Abordagem Estratégica - 2ª Edição - Ed. Bookman - 2009.
The identical small spheres shown in Figure 71-09.1 are loaded with +100 nC
and -100 nC. They are suspended, as shown, in the presence of a module electric
field equal to 100,000 N/C. What is the mass of each sphere?
An electric pendulum of length R and mass m = 2 Kg electrified with a
positive charge Q , is repelled by another equal charge, fixed at point A.
Figure 71-10.1 shows the equilibrium position of the pendulum.
Considering g = 10 m/s2, find the charges module.
Problem 71-11
Source: Entrance Exam PUCRJ - RJ - 2009.
Two identical spheres, charged with charges Q = 30 µC, are suspended from
from the same point by two insulating wires of the same length as shown in Figure 71-11.1.
In balance, the angle formed by the two insulating wires with the vertical is 45°.
Knowing that the mass of each sphere is m = 1 Kg and considering the Coulomb constant
K = 9 x 109 N m2/C2, determine the distance between the two
spheres when in balance. Consider g = 10 m/s2.
