Most physicists do not actually believe that mass depends on velocity as in the relativistic mass formula, but still keep this concept, for instance because an identical formula, energy-momentum relation, is seen as useful. However, there is no sense in keeping false concepts and valid results that have been derived by using false arguments can also be derived in other ways, even in a correct way. Yet, if an alternative explanation is proposed, it would be good to get a proposal for an experiment that can support the new explanation.The presented article discusses experiments that could add strength to the explanation thatrelativistic mass is actually a wrong interpretation of force becoming weaker if the object of the force is escaping the force with nearly the propagation speed of the force. The article considers if such an experiment could be done with a vacuum tube but no experimental results are given yet in this paper.