The magnitude of the resultant force is given by the centripetal force, since the car is under a circular motion. So, we have:

The centripetal acceleration is given by:

Where v is the linear speed and r the radius of the circular motion. Replacing this and solving:

Answer:
a) C = 4,012 10⁻¹⁴ F, b) Q = 1.6 10⁻¹¹ C
, c) U = 3.21 10⁻¹¹ J
Explanation:
a) The capacitance of a capacitor is
C = k e₀ A / d
Let's calculate
C = 4 8.85 10⁻¹² 17 10⁻⁴ / 0.150 10⁻²
C = 4,012 10⁻¹⁴ F
b) let's look the charge
C = Q / ΔV
Q = C ΔV
Q = 4,012 10⁻¹⁴ 400
Q = 1.6 10⁻¹¹ C
c) The stored energy
U = ½ C ΔV²
U = ½ 4,012 10⁻¹⁴ 400²
U = 3.21 10⁻¹¹ J
Answer: The electric repulsion between the two protons is stronger than the gravitational attraction.
Explanation: Please see the attachments below