Answer:
Let the mass of the book be "m", acceleration due to gravity be "g", velocity be "v" and height be "h".
Now if we are holding a book at a certain height (h), <em><u>the potential energy will be maximum which is equal to mass× acceleration due to gravity× height (= mgh)</u>.</em>
(Remember: kinetic energy =0)
Now we consider that the book is dropped, in this case a force will act downward towards the centre of the earth, <em><u>Force= mass× acceleration due to gravity (F=mg)</u></em>. It is equal to the weight of the book.
While the book is falling, the potential energy stored in the book converts into kinetic energy and strikes the floor with <em><u>the maximum kinetic energy= (1/2)×mass×velocity² (=1/2mv²)</u>.</em>
(Remember: kinetic energy=0)
Due to this process the whole energy is conserved.
As the potential energy decreases kinetic energy increases.
<span>increased evaporation</span>
Answer:
2.30 × 10⁻⁸ N if the two electrons are in a vacuum.
Explanation:
The Coulomb's Law gives the size of the electrostatic force 
between two charged objects:
,
where
is coulomb's constant. 
in vacuum.
and 
are the signed charge of the objects.
is the distance between the two objects.
For the two electrons:
.
.
.
The sign of is negative. In other words, the two electrons repel each other since the signs of their charges are the same.
