A 120-m long copper wire (resistivity 1.68 10-8 m) has ...

[krzymel]

A 120-m long copper wire (resistivity 1.68  10-8 m) has resistance 6.0 . What is the diameter of the wire?
 
  A)
 
  0.065 mm
  B)
 
  0.65 mm
  C)
 
  0.65 cm
  D)
 
  0.65 m
  E)
 
  6.5 m

Question 2

A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth,
 
  Andrea rides on a spaceship which travels away from Earth at a speed of 0.60c for five years (as measured by Courtney), then immediately turns around and comes back at 0.60c. When Andrea returns, Courtney is 20 years old. How old is Andrea upon her return?
  A) 20 y B) 15 y C) 12 y D) 10 y E) 18 y

[momolu]

Answer to Question 1

B

Answer to Question 2

E

[krzymel]

Gracias!

[apple]

Wow, this really help