Final answer:
Using Coulomb's Law, the electric force between two charges of 4.7×10−9 C and -3.1×10−9 C separated by 0.020m is calculated to be -1.55N, indicating an attractive force.
Step-by-step explanation:
The electric force between two point charges can be determined using Coulomb's Law, which is given by the formula F = k |q1q2| / r2, where F is the force between the charges, q1 and q2 are the magnitudes of the charges, r is the distance between the charges, and k is Coulomb's constant (approximately 8.99 × 109 N m2/C2).
In this problem, the charges are 4.7 × 10−9 C and −3.1 × 10−9 C, and they are separated by a distance of 0.020 m. Applying Coulomb's Law:
F = (8.99 × 109 N m2/C2) |(4.7 × 10−9 C)(−3.1 × 10−9 C)| / (0.020 m)2
Because one charge is negative and forces between unlike charges are attractive, the force will be negative, indicating attraction. Using the absolute values for the calculation but keeping the sign in mind for the direction:
F = −(8.99 × 109) (4.7 × 10−9)(3.1 × 10−9) / (0.020)2
F = −1.55 N
The correct answer is (d) −1.55 N. The force is attractive and has a magnitude of 1.55 newtons.