Solution :
We assume that there is a ring having a charge +Q and radius r. Electric field due to the ring at a point P on the axis is given by :




If we put an electron on point P, then force on point e is :

![F= \frac{-eKQx}{(r^2+x^2)^{3/2}}= \frac{-eKQx}{r^3[1+\frac{x^2}{r^2}]^{3/2}}](https://tex.z-dn.net/?f=F%3D%20%5Cfrac%7B-eKQx%7D%7B%28r%5E2%2Bx%5E2%29%5E%7B3%2F2%7D%7D%3D%20%5Cfrac%7B-eKQx%7D%7Br%5E3%5B1%2B%5Cfrac%7Bx%5E2%7D%7Br%5E2%7D%5D%5E%7B3%2F2%7D%7D)
If r >> x , then 
Then, 


Compare, a = -ω²x
We get,




The term used is " WORK".
I'm really sorry it's not one of the choices.
Answer: 4.7rad
Explanation:
Angular displacement =s/r
Where s=distance traveled
r=radius
Angular displacement =141m/30m
Angular displacement =4.7rad.
Answer:
The magnitude of the magnetic field B is 5.921 T.
Explanation:
Given that,
Length = 4.1 mm



Current 
We need to calculate the magnetic field
Using formula of magnetic field

Put the value into the formula


Hence, The magnitude of the magnetic field B is 5.921 T.