Explanation:
It is given that,
Velocity of the electron, 
Magnetic field, 
Charge of electron, 
(a) Let
is the force on the electron due to the magnetic field. The magnetic force acting on it is given by :

![F_e=1.6\times 10^{-19}\times [(2\times 10^6i+3\times 10^6j)\times (0.030i-0.15j)]](https://tex.z-dn.net/?f=F_e%3D1.6%5Ctimes%2010%5E%7B-19%7D%5Ctimes%20%5B%282%5Ctimes%2010%5E6i%2B3%5Ctimes%2010%5E6j%29%5Ctimes%20%280.030i-0.15j%29%5D)


(b) The charge of electron, 
The force acting on the proton is same as force on electron but in opposite direction i.e (-k). Hence, this is the required solution.
Answer:
1807.56 kJ
Explanation:
Parameters given:
Current, I = 8.9A
Time, t = 4.7hrs = 4.7 * 3600 = 16920 secs
Voltage, V = 12V
Electrical energy is given as:
E = I*V*t
Where I = Current
V = Voltage/Potential differenxe
t = time in seconds.
E = 8.9 * 12 * 16920
E = 1807056 J = 1807.056 kJ
The energy absorbed by photon is 1.24 eV.
This is the perfect answer.
To solve this problem we will derive the expression of the precession period from the moment of inertia of the given object. We will convert the units that are not in SI, and finally we will find the precession period with the variables found. Let's start defining the moment of inertia.

Here,
M = Mass
R = Radius of the hoop
The precession frequency is given as

Here,
M = Mass
g= Acceleration due to gravity
d = Distance of center of mass from pivot
I = Moment of inertia
= Angular velocity
Replacing the value for moment of inertia


The value for our angular velocity is not in SI, then


Replacing our values we have that


The precession frequency is




Therefore the precession period is 5.4s