How much weigh a pound in gravitational field
  The force in the equation of motion of a particle should be in accordance with energy conservation in a constant gravitational field. It turns out that this is possible only if the force is given by the change of momentum per unit of coordinate (not proper) time. We discuss the consequences of this fact. In particular it turns out that the spring balance, which keeps the body at rest in (strong) gravitation field, shows the finite value even at infinitely close approach to horizons of black holes, if they exist in Nature. 
A.I Nikishov
physics.gen-ph