PART A)
Electrostatic potential at the position of origin is given by

here we have



now we have


Now work done to move another charge from infinite to origin is given by

here we will have

so there is no work required to move an electron from infinite to origin
PART B)
Initial potential energy of electron




Now we know



now by energy conservation we will have
So here initial total energy is sufficient high to reach the origin
PART C)
It will reach the origin
The freezing point ..... :)
A uniform thin solid door has height 2.20 m, width .870 m, and mass 23.0 kg. Find its moment of inertia for rotation on its hinges. Is any piece of data unnecessary? So far, I don't understand how to calculate moments of inertia for things like this at all. I can do a system of particles, but when it comes to any ridgid objects, such as this door or rods or cylinders, I don't get it. So basically I have no idea where to even start with this.
so A
Answer: 10.58 C has flowed during the lightning bolt
Explanation:
Given that;
Time of flow t = 1.2 × 10⁻³
perpendicular distance r = 21 m
Magnetic field B = 8.4 x 10⁻⁵ T
Now lets consider the expression for magnetic field;
B = u₀I / 2πr
the current flow is;
I = ( B × 2πr ) / u₀
so we substitute
I = ( (8.4 x 10⁻⁵) × 2 × 3.14 × 21 ) / 4π ×10⁻⁷
= 0.01107792 / 0.000001256
= 8820 A
Hence the charge flows during lightning bolt will be;
q = It
so we substitute
q = 8820 × 1.2 × 10⁻³
q = 10.58 C
therefore 10.58 C has flowed during the lightning bolt