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 
Answer:
Explanation:
1st one
What is your evidence?
Very heavy professional or restaurant pans will have iron handles, while those for home use will be made of brass or stainless steel. All are perfectly safe for oven use.
Your answer is C) The year the element was discovered :)
I would say a. Good luck!
Answer:
The Physical Behavior of Objects when Gravity is Missing
In order to be able to form a concept of the general physical conditions existing in a weightless state, the following must be noted: the force of the Earth's gravity pulling all masses down to the ground and thus ordering them according to a certain regularity is no longer active.