Calculating the Kinetic Energy of a Point Charge From Far Away

[brandif22]

Homework Statement

Four point charges form a square with sides of length d. Use k as the constant instead of 1/4*pi*epsilon not.

+q_______-3q



+2q______+5q

What would be the kinetic energy for 2q at a very large distance from the other charges? Express answer in terms of q, d, and appropriate constants.

Homework Equations

U=kqq/r , K=1/2mv^2

The Attempt at a Solution

I'm assuming that since the charge is a large distance away, there would be no kinetic energy acting on the charge 2q since it is far away from the forces of the other 3 charges.

 

[anathema]

Therefore, the kinetic energy would be 0. However, if we were to consider the potential energy, it would be U=k(2q)(-3q)/d + k(2q)(5q)/d + k(2q)(q)/d = -5kq^2/d.

 

[Moetasim]

Therefore, the kinetic energy would be zero. However, if we assume that the charge is moving towards or away from the other charges, then we can use the equation K=1/2mv^2 to calculate the kinetic energy. We would need to know the mass of the charge 2q and its velocity in order to solve for the kinetic energy. The distance between the charges would also play a role in the calculation, as it would affect the strength of the electrostatic force between the charges. We would also need to use the constant k instead of 1/4*pi*epsilon not in the calculation. Overall, the expression for the kinetic energy would involve the variables q, d, k, m, and v.