Answer:
Rate of change of magnetic field is
Explanation:
We have given diameter of the circular loop is 13 cm = 0.13 m
So radius of the circular loop 
Length of the circular loop 
Wire is made up of diameter of 2.6 mm
So radius 
Cross sectional area of wire 
Resistivity of wire 
Resistance of wire 
Current is given i = 11 A
So emf 
Emf induced in the coil is 


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 
Power = work/time = (Force times distance)/time
= (30N *10.0m)/5.00s = 300/5 = 60 Watts
Option D is correct. An arch carries the thrust of weight to its <u>sides </u>with a <u>post-and-lintel.</u>
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<h3>What is an arch?</h3>
An arch is indeed a vertical curving construction that covers an elevated space that may or may not sustain the load above it or the pressure gradient against it
In the case of a horizontally arched, such as an embankment dam. While arches and vaults are often confused, A vault is defined as an ongoing arch forming a roof.
Option D satisfies the fill-in blanks option.
Hence option D is correct. An arch carries the thrust of weight to its <u>sides </u>with a <u>post-and-lintel.</u>
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To learn more about the arch refer to the link;
brainly.com/question/18162421