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: Phillipe wins the race
Explanation:
Given
Length of track=20 m
Velocity of Phillippe=2 m/s w.r.t sidewalk
Velocity of sidewalk=1.5 m/s
Rena velocity=2 m/s
Therefore absolute velocity of P is 2+1.5=3.5 m/s
Time taken by phillippe 
=5.714+10=15.714 s
Time taken by rena
as the time taken by phillippe is less than rena therefore Phillippe wins the race.
It kinda makes sense that it would be considered a metamorphosis.
Answer:
Angle of reflection of light is 34 degree
Explanation:
As per law of reflection of light we know that
angle of incidence of light = angle of reflection of light
So here we know that
angle of incidence on the surface of oil is given as
so we know that
so here we can say that reflection angle of light will be same as angle of incidence
