This consideration is concerned with the effect of a given gravitational field on a sample body and not with the contributions made by gravitational sources according to the energy-momentum tensor. The special theory of relativity is therefore sufficient for the investigation in local approximation.a) Using the example of a movement in the direction of a gravitational field, it is shown that either the equivalence principle applies only approximately or gravity does not act on the mass but on the energy of falling bodies.b) If the equality of gravity and inertia is also to apply to bodies with internal kinetic and potential energies, then gravity is proportional to the respective energy of the individual components. Otherwise, gravity and inertia would only be approximately equal.The proportionality is transferred to the energy of the entire body despite any internal velocities.c) The planetary motion suggests a velocity-dependent gravitational force, from which the exact validity of the equivalence principle follows as well as the exact equality of gravity and inertia, even taking into account special relativistic effects.d) Newton's law of gravitation for two masses can be formulated in special relativistic terms by replacing their product with the scalar product of the "mass tangential vectors" to the world lines. This is a conclusion that is possible without recourse to general relativity.e) Short reference to the difference between the gravitational field and the electrostatic field, the force of which is independent of velocity.