module StringTensions

# File lib/string_tensions.rb, line 27
def self.freq_from_pitch(pitch)
  NoteFrequencies.frequency_from_name(pitch)
end

# File lib/string_tensions.rb, line 9
def self.tension(uw_lbs_inch, length_in_inches, freq)
  # T (Tension) =  (UW  x (2 x L x F)**2) / 386.4
  (uw_lbs_inch * (2 * length_in_inches * freq)**2) / K
end

# File lib/string_tensions.rb, line 14
def self.tension_for_pitch(uw_lbs_inch, length_in_inches, pitch)
  tension(uw_lbs_inch, length_in_inches, freq_from_pitch(pitch))
end

# File lib/string_tensions.rb, line 18
def self.uw(tension_lbs, length_inches, freq)
  # UW (unit weight) =  (T x 386.4) / (2 x L x F)**2
  ((tension_lbs * K) / (2 * length_inches * freq)**2).to_f
end

# File lib/string_tensions.rb, line 23
def self.uw_for_pitch(tension_lbs, length_inches, pitch)
  uw(tension_lbs, length_inches, freq_from_pitch(pitch))
end