Explanation:
to determine if important scientific results are repeatable
The answer is “Family”
Explanation- There are 18 numbered groups in the periodic table. The elements in a group have similar physical or chemical characteristics and some groups have a specific name, for example group 17 (the halogens).
Your answer is C) <span> the potential energy of an object is always greater than its kinetic energy </span>
To develop this problem it is necessary to apply the concepts related to Gravitational Potential Energy.
Gravitational potential energy can be defined as

As M=m, then

Where,
m = Mass
G =Gravitational Universal Constant
R = Distance /Radius
PART A) As half its initial value is u'=2u, then



Therefore replacing we have that,

Re-arrange to find v,



Therefore the velocity when the separation has decreased to one-half its initial value is 816m/s
PART B) With a final separation distance of 2r, we have that

Therefore




Therefore the velocity when they are about to collide is 