A small body of super dense material whose mass is twice the mass of the earth but size is very small when compared with the earth. If it starts from the state of rest, we need to know its location after a specified time. The problem is as shown in the diagram below.

A small body of super dense material whose mass is twice the mass of the earth but size is very small when compared with the earth. If it starts from the state of rest, we need to know its location after a specified time. The problem is as shown in the diagram below.

Solution

For every action there is equal and opposite reaction. As the body comes downward, the earth moves upward. The two meet at the center of mass of the system. We can further solve the problem as shown in the diagram below.