Answer:
a)The approximate radius of the nucleus of this atom is 4.656 fermi.
b) The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527
Explanation:

= Constant for all nuclei
r = Radius of the nucleus
A = Number of nucleons
a) Given atomic number of an element = 25
Atomic mass or nucleon number = 52


The approximate radius of the nucleus of this atom is 4.656 fermi.
b) 
k=
= Coulombs constant
= charges kept at distance 'a' from each other
F = electrostatic force between charges


Force of repulsion between two protons on opposite sides of the diameter



The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527
You can do animals that have 4 legs (dogs, horses), animals that fly (parrot, eagle), animals that live in the water (goldfish,bass)
factorise 1/10^2 out of both.
add 1/4.5 to 1/9.4 .... common denominator 4.5x9.4
multiply result by 1/10^2
find reciprocal of result
phew !
<h2>Answer: remain stationary</h2>
Stationary waves (so called because they seem to be immobile) occur when two waves interfere with the <u>same frequency, amplitude but with different direction</u>, along a line with a phase difference of half wavelength.
In this kind of waves there are two types of points:
The nodes, which are points that remain motionless or stationary and do not vibrate. They are due to the destructive interference of both waves when they meet.
The antinodes, which are points that vibrate with a maximum vibration amplitude. They are due to the non-destructive interference of both waves.
According to this explanation and comparing it with the description, when this two waves pass through each other, the point P will become a node, hence<u> it will remain stationary</u>.