# A charge of 2 C is at (-3,7) and a charge of -1 C is at ( 2, -9 ). If both coordinates are in meters, what is the force between the charges?

Oct 5, 2016

#### Answer:

F ~~ -6.40×10^7 N where negative indicates an attractive force.

#### Explanation:

Let's look up Coulomb's Law and its associated constant:

F = k_e(q_1q_2)/(r²)

Where k_e = 8.99×10^9 Nm²C^-2

We use the given points to compute the square of the distance between the charges:

r² = (2 - -3)² + (-9 - 7)²

r² = (5)² + (-16)²

r² = (5)² + (-16)²

r² = 25 + 256

r² = 281 m^2

F = ((8.99×10^9 Nm²C^-2)(2 C)(-1 C))/(281 m^2)

F ~~ -6.40×10^7 N