Explanation:
It is given that,
The time period of artificial satellite in a circular orbit of radius R is T. The relation between the time period and the radius is given by :

The radius of the orbit in which time period is 8T is R'. So, the relation is given by :



So, the radius of the orbit in which time period is 8T is 4R. Hence, this is the required solution.
Its the answer b, because oil has a great density, therefore, when you mix them together the oil will be below and the above of it.
Lower than 7 is acid greater than 7 is a base
It is know as the normal force.
When a solid is placed on a support, the latter exerts forces on the solid at each point of contact. These are forces that oppose the weight and prevent an object from falling.
This force is usually vertical and upward and often offsets the weight. If the solid is in equilibrium on the support the forces compensate the weight of the solid.