Answer:
Explanation:
Coulomb's law states that the force of attraction or repulsion between any two charges is proportional to the product of the magnitude of charges and inversely proportional to the square of the distance between the charges
⇒
∴
where
is the force of attraction or repulsion
is Coulumb's constant=
and
are the magnitude of the charges
is the distance between two charges
The force between the two charges is attractive if they are of different polarity
The force between the two charges is repulsive if they are of same polarity
Question 7:
Given:
, 
By coulomb's law,

⇒
Question 6:
Given:
, 
By coulomb's law,

⇒
I don't think an object can exert a force on itself.
Try it: Get up on a skateboard, and see if you can do anything to yourself that makes you start moving ... without touching anything else.
It'll be easy to tell if you succeed. If you actually do exert an unbalanced force on yourself, then you'll begin to accelerate.
Greater water pressure acts on the bottom than on the top
La magnitud es de 9.8 m/s² ... la aceleración de la gravedad en o cerca de la superficie de la Tierra.
La dirección es hacia el centro de la Tierra. (Llamamos a esa dirección "abajo").