sentences:  The general solution for the pressure distribution in the contact area in the JKR model is
  
  Note that in the original Hertz theory, the term containing formula_171 was neglected on the ground that tension could not be sustained in the contact zone.For contact between two spheres
  
  where formula_173 is the radius of the area of contact, formula_4 is the applied force, formula_164 is the total surface energy of both surfaces per unit contact area,
  formula_176 are the radii, Young's moduli, and Poisson's ratios of the two spheres, and
  
  The approach distance between the two spheres is given by
  
  The Hertz equation for the area of contact between two spheres, modified to take into account the surface energy, has the form
  
  When the surface energy is zero, formula_180, the Hertz equation for contact between two spheres is recovered.When the applied load is zero, the contact radius is
  
  The tensile load at which the spheres are separated (i.e., formula_182) is predicted to be
  
  This force is also called the pull-off force.