A cubical box of side 1 m contains helium gas (atomic weight 4) at a pressure of   100 Nm–2. During an observation time of 1 second, an atom travelling with root- mean-square speed parallel to one of the edges of the cube was found to make  500 hits with a particular wall, without any collision with other atoms. Take R =  253  J mol–1K–1  and k = 1.38×10–23J K–1. Evaluate average kinetic energy.