Question

A charge of 7.1 x 10-4 C is placed at the origin of a Cartesian coordinate system. A second charge of 6.5 x 10-4 C lies 20 cm above the origin, and a third charge of 8.9 x 10-4 C lies 20 cm to the right of the origin. Determine the direction of the total force on the first charge at the origin. Express your answer as a positive angle in degrees measured counter clockwise from the positive x-axis.

Answer 1

α = 36.21 °

β = 143.79°

Step-by-step explanation:

To do this, we need to know the expression to calculate the angle.

In this case:

α₁ = tan⁻¹ (Fy₁/Fx₁) (1)

Now, let's analize the given data.

We have a charge q₁ at the origin of the cartesian coordinate system, so, it's at the 0. The charge q₂ is 20 cm above q₁, meaning is on the y-axis. Finally q₃ it's 20 cm to the right, meaning it's on the x-axis.

Knowing this,we can calculate the force that q₂ and q₃ are exerting over q₁. As these forces are in the x and y-axis respectively, we also are calculating the value of the forces in the x and y axis, that are needed to calculate the direction.

The expression to calculate the force would be Coulomb's law so:

F = K q₁q₂ / r² (2)

The value of K is 9x10⁹ N m² / C². Let's calculate the forces:

F₁₂ = Fy = 9x10⁹ * (7.1x10⁻⁴) * (6.5x10⁻⁴) / (0.020)²

Fy = 1.04x10⁷ N

F₁₃ = Fx = 9x10⁹ * (7.1x10⁻⁴) * (8.9x10⁻⁴) / (0.020)²

Fx = 1.42x10⁷ N

Now that we have both forces, we can calculate the magnitude of the force:

F = √(Fx)² + (Fy)²

F = √(1.04x10⁷)² + (1.42x10⁷)²

F = 1.76x10⁷ N

Finally, the direction would be applying (1):

α = tan⁻¹ (1.04x10⁷/1.42x10⁷)

α = 36.21 °

And counter clockwise it would be:

β = 180 - 36.21 = 143.79°

Hope this helps