The answer is neutral charge. An atom element will always and has to be stable, in order for this state to happen. The charge of an electron has to be neutral. For atom with neutral charge, the proton will always equal the number of electron.
Answer:
1. Torque → F. Study of forces
2. C.O.G → D. Point of action of weight.
3. Plumb line → A. Line of C.O.G
As we know that KE and PE is same at a given position
so we will have as a function of position given as

also the PE is given as function of position as

now it is given that
KE = PE
now we will have




so the position is 0.707 times of amplitude when KE and PE will be same
Part b)
KE of SHO at x = A/3
we can use the formula

now to find the fraction of kinetic energy



now since total energy is sum of KE and PE
so fraction of PE at the same position will be


(a) Period of the wave
The period of a wave is the time needed for a complete cycle of the wave to pass through a certain point.
So, if an entire cycle of the wave passes through the given location in 5.0 seconds, this means that the period is equal to 5.0 s: T=5.0 s.
(b) Frequency of the wave
The frequency of a wave is defined as

since in our problem the period is

, the frequency is

(c) Speed of the wave
The speed of a wave is given by the following relationship between frequency f and wavelength

: