Answer:
3.974 Joule
Explanation:
Diameter of ring = 7.7 cm
a = Distance from the center = d/2 = 3.85 cm = 0.0385 m
Q = Charge = 5 mC
q = Charge to move = 3.4 mC
k = Coulomb constant = 9×10⁹ Nm²/C²
Work done will be equal to Potential energy when mass is at center

∴ Work to move a tiny 3.4 mC charge from very far away to the center of the ring is 3.974 Joule
Sedimentary rock I believe
Answer:
Fr = 48 [N] forward.
Explanation:
Suppose the movement is on the X axis, in this way we have the force of the engine that produces the movement to the right, while the force produced by the brake causes the vehicle to decrease its speed in this way the sign must be negative.
∑F = Fr
![F_{engine}-F_{brake} =F_{r}\\F_{r}=79-31\\F_{r}=48[N]](https://tex.z-dn.net/?f=F_%7Bengine%7D-F_%7Bbrake%7D%20%3DF_%7Br%7D%5C%5CF_%7Br%7D%3D79-31%5C%5CF_%7Br%7D%3D48%5BN%5D)
The movement remains forward, since the force produced by the movement is greater than the braking force.