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:
- quality factor (Q) = 69.99
- inductor = 1.591 x 10⁻⁴ H
- capacitor = 3.248 x 10⁻¹⁰ F
Explanation:
Given;
resonance frequency (F₀) = 700 kHz
resistor, R = 10 Ohm
bandwidth (BW) = 10 kHz
bandwidth (BW) 

make L (inductor) the subject of the formula


make C (capacitor) the subject of the formula

quality factor (Q) 
quality factor (Q) = 69.99
A. inelastic, since the girl moves in the same direction as the thrown ball
Answer: A
Explanation:
Molecules speed up as heat is added
For example when water is heated as the water gets hotter the molecules speed up causing the water to boil and change phases into a gas (this is called evaporation)
In an ice cube the water molecules are frozen (barely moving compressed tight together) as the ice cube heats up the molecules start speeding up and moving further apart as the ice cube turns into liquid form. So as heat is added molecules speed up, move faster and spread further apart