Answer:
Velocity of the electron at the centre of the ring, 
Explanation:
<u>Given:</u>
- Linear charge density of the ring=

- Radius of the ring R=0.2 m
- Distance of point from the centre of the ring=x=0.2 m
Total charge of the ring

Potential due the ring at a distance x from the centre of the rings is given by

The potential difference when the electron moves from x=0.2 m to the centre of the ring is given by

Let
be the change in potential Energy given by

Change in Potential Energy of the electron will be equal to the change in kinetic Energy of the electron

So the electron will be moving with 
Answer:
(35 N - 10 N)/8kg = 3.125 m/s^2
Explanation:
The formula for Force is:
Force = Mass*Acceleration
(Force is equal to Mass times Acceleration)
Since we're told to find the acceleration of the box. We make acceleration the subject of the equation:
Acceleration = Force/Mass
(Acceleration equal to Force divided by Mass)
We know that the force are 35 N forward and 10 N backward, and the weight of the box is 8kg.
= (35 N - 10 N)/8kg
The reason that 35 N minus 10 N is because the 10 N is pushing the box backward.
= 25 N/8kg
= 3.125 m/s^2
Hope it helps :DD
the answer is definitely A.