so the monster passige may be confusing so just do auto books
Lenz's Law: The polarity of the induced emf is such that it produces a current whose magnetic field opposes the change in magnetic flux through the loop.
Answer:

Explanation:
Given that,
Magnetic force acting on an electron, 
The magnitude of the magnetic field,
We need to find the magnitude of the velocity. We know that the magnetic force is given by :

Where
v is the velocity
So,

So, the magnitude of velocity is
.
Answer:
Time = 6 years
Explanation:
First, we will calculate the no. of half life periods required to reduce the mass of Protactinium to the given value:

where,
n = no. of half-life periods = ?
m = initial mass = 86.3 g
m' = remaining mass = 10.8 g
Therefore,

Since the bases are the same. Therefore equating powers:
n = 3
Now we calculate the time:

<u>Time = 6 years</u>