Units of Coulomb, trouble understanding the question

[JFonseka]

Homework Statement

Two charges, q1 = 4.9 e C and q2 = -3.6 e C are located 105nm apart, what is the size of the force between the two charges?

Homework Equations

F=kqq/r^2

The Attempt at a Solution

I did it according to the formula and I got the answer wrong, so I checked it using an online force calculator between charges, and it gave the same answer I initially got. I looked up what e C is, thinking maybe it's indicating something smaller than 1 C, and couldn't really find a graduation for that, what am I doing wrong? Is it meant to be multiplied by 1.6 x 10^-19?

 

[mathfeel]

Actually $q_1 = 4.9 e C$ is somewhat incorrect. $e = 1.6\times10^{-19}C$ is the elementary charge and already contain the unit Coulomb. So it is as if $q_1$ has unit Coulomb-Coulomb.

 

[JFonseka]

Actually $q_1 = 4.9 e C$ is somewhat incorrect. $e = 1.6\times10^{-19}C$ is the elementary charge and already contain the unit Coulomb. So it is as if $q_1$ has unit Coulomb-Coulomb.

So does this mean that I have to multiply 4.9 by 1.6x10^-19?

 

[JFonseka]

Nvm, problem(s) solved.

 

[rwisz]

As a scientist, it is important to always check your work and verify your calculations. It is also important to clarify any confusion or misunderstandings in order to accurately solve the problem.

The unit of Coulomb (C) is a unit of electric charge. The letter "e" in this context most likely refers to the elementary charge, which is equal to 1.6 x 10^-19 C. Therefore, q1 = 4.9 e C would be equivalent to 4.9 x 1.6 x 10^-19 C.

In order to calculate the force between the two charges, you will need to use the value of the elementary charge in your calculations. The correct formula to use is F=kq1q2/r^2, where k is the Coulomb's constant (9 x 10^9 Nm^2/C^2), q1 and q2 are the charges in Coulombs, and r is the distance between the charges in meters.

Using this formula, the force between the two charges would be:

F = (9 x 10^9 Nm^2/C^2) x (4.9 x 1.6 x 10^-19 C) x (-3.6 x 1.6 x 10^-19 C) / (105 x 10^-9 m)^2

= -2.6 x 10^-16 N

It is possible that the online force calculator you used did not take into account the units of Coulomb, which may have led to a different answer. It is always important to pay attention to units and make sure they are consistent throughout your calculations.

Additionally, it is important to note that the negative sign in the answer indicates that the force is attractive, as the two charges have opposite signs.

In conclusion, the size of the force between the two charges is -2.6 x 10^-16 N. It is important to double check your calculations and make sure you are using the correct units in order to accurately solve the problem.