2ways friction is and 2 ways it does not

Benefits of friction.

1. Walking. Friction between the soles of our  shoes and the ground enables us to walk. The sole of the shoe is held to the ground through friction. This is what is termed as "grip" of the shoe. The more grip a shoes offers, the better and faster we can walk.

2. Writing. Writing using a pen requires friction. It is impossible to hold a pen in the hand without friction because it would slip out. Also the graphite point of the pencil would not make a mark on the paper without friction.

Drawbacks of friction

1. Drag. An aircraft taking off experiences significant friction between it and the air resulting in drag, so much fuel has to be used to  create energy to overcome the wind resistance.

2. Surface hindrance. Friction makes moving something heavy from  one part of a room to another very difficult. Sliding a large box across the flour takes a lot of energy due to friction between the box and the floor.

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.