Answer:
The distance of the father from the center is  [tex]d_f = \frac{1}{2} \ m[/tex]
Explanation:
From the question we are told that
  The distance of the son from the center is  [tex]d_s = 2 \ m[/tex]
Â
Let the mass of the son be  [tex]m_s[/tex]
   then the mass of the father is  [tex]m_f = 4m_s[/tex]
Now for the teeter-totter to be balanced the torque due to the weight of the father must be equal to the torque due to the weight the son, this is mathematically represented as
     [tex]\tau_s = \tau_f[/tex]
Where  [tex]\tau_s[/tex] is the torque of the son which is mathematically represented as
    [tex]\tau_ s = m_s * d_s * g[/tex]
while [tex]\tau_f[/tex] is the torque of the father which is mathematically represented as
    [tex]\tau_f = m_f * d_f * g[/tex]
=> Â Â [tex]\tau_f = 4 m_s * d_f * g[/tex]
 So
     [tex]4 m_s * d_f * g = m_s * d_s * g[/tex]
substituting values
    [tex]4 * d_f * = 2[/tex]
 =>   [tex]d_f = \frac{1}{2} \ m[/tex]   Â