Posted by Liliana on .
the equatorial radius of the earth is approximately 3960 miles. suppose a wire is wrapped tightly around the earth at the equator. how much must this wire be lengthened if it is to be strung on 10 feet poles above the ground? (1 mile=5280 feet)
delta y= dy/dx (2pir) * deltax
delta y= 2pi * 10/5280
delta y= 20pi/5280
is this right or no? thanks

SolvedCalculusPlease check? 
Reiny,
No Calculus needed for this
circumference of earth = 2π(radius) = 2πr
radius of earth with string around it = r+10
circumference with string = 2π(r+10)
= 2πr + 20π
so the increase in the length of string
= 20π ft or appr 62.8 ft
notice the data given was not even necessary.