Answer:
Part A) Electric fields at the designated point due to charges q₁ and q₂:
E₁ = 33.75 * 10³ N/C (-j), E₂ = (6.48 (-i) + 8.64 (+j)) * 10³ N/C
Part B) The overall electric field at P (Ep)
Ep = (6.48 * 10³ (-i) + 25.11 * 10³ (-j)) N/C
Explanation:
Conceptual analysis
The electric field at point P caused by a point charge is calculated as:
E = k*q/d²
E: Electric field measured in N/C
q: charge magnitude in Newtons (N)
k: electric constant measured in N*m²/C²
d: distance from the charge q to point P in meters (m)
Equivalence:
1 nC = 10⁻⁹ C
1 cm = 10⁻² m
Data:
k = 9 * 10⁹ N*m²/C²
q₁ = -6.00 nC = -6 * 10⁻⁹ C
q₂ = +3.00 nC = +3 * 10⁻⁹ C
d₁ = 4 cm = 4 * 10⁻² m

d₂ = 5 * 10⁻² m
Part A) Calculation for electric fields at point from q₁ and q₂:
Refer to the attached illustration:
E₁: Electric Field at point P(0,4) cm due to charge q₁. Since q₁ is negative (q₁-), the electric field approaches the charge.
E₂: Electric Field at point P(0,4) cm due to charge q₂. Since q₂ is positive (q₂+), the electric field emanates from the charge.
E₁ = k*q₁/d₁² = 9 * 10⁹ * 6 * 10⁻⁹ / (4 * 10⁻²)² = 33.75 * 10³ N/C
E₂ = k*q₂/d₂²= 9 * 10⁹ * 3 * 10⁻⁹ / (5 * 10⁻²)² = 10.8 * 10³ N/C
E₁ = 33.75 * 10³ N/C (-j)
E₂x = E₂cosβ = 10.8 * (3/5) = 6.48 * 10³ N/C
E₂y = E₂sinβ = 10.8 * (4/5) = 8.64 * 10³ N/C
E₂ = (6.48 (-i) + 8.64 (+j)) * 10³ N/C
Part B) Calculation for net electric field at P (Ep)
The electric field at point P from multiple point charges is the vector sum of the individual electric fields.
Ep = Epx (i) + Epy (j)
Epx = E₂x = 6.48 * 10³ N/C (-i)
Epy = E₁y + E₂y = (33.75 * 10³ (-j) + 8.64 * 10³ (+j)) N/C = 25.11 * 10³ (-j) N/C
Ep = (6.48 * 10³ (-i) + 25.11 * 10³ (-j)) N/C
Ep = (6.48 * 10³ (-i) + 25.11 * 10³ (-j)) N/C