What is the potential difference V?

3. A helium nucleus is accelerated from rest through a potential difference V to a kinetic energy of X ∙ 10⁻¹³ J. 

What is the potential difference V?
X is some number.

Answer:

V = E/q = E/(2e) = X ∙ 10⁻¹³ J / (2∙1.60×10⁻¹⁹ C) = 0.312X MV

Three Point Charges

1. Three point charges are positioned as follows: q₁ is at (x₁ m, y₂ m), q₂ is at (x₂ m, y₂ m), and q₃ is at (x₂ m, y₃ m). If q₁ = b₁ μC, q₂ = b₂ μC, and q₃ = b₃ μC, what is the magnitude of the force on q₂?

x₁, y₂, x₂, y₃, b₁, b₂, and b₃ are some numbers.

Answer:

|F(q₂)| = kq₂ ( (q₁/r₁²)²+(q₃/r₃²)² )⁰·⁵ =
= 8.99·10⁻³ ( (b₁/(x₂-x₁)²)²+(b₃/(y₃-y₂)²)² )⁰·⁵ N