I was listening to one of the debates related to politics by one of the influential persons in the current times. He was talking about the ideologies and the promises he had made on the basis of those ideologies. He also showed the achievements which he had received highlighting that he had fulfilled his promises. His debates were backed up with the facts and the figures in the recent times and thus he was proved right. There was no pompous show in his debate.

I uploaded the answer to a file hosting. Here's link:

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d.) circle motion requires a force to give it a centripetal acceleration.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.