Friction on snow and ice

An experimental study has been made of the friction of real ski and of smaller models sliding on snow and ice at various temperatures. On cold snow the static friction is high. When the sliding speed is appreciable the friction falls to a low value, and experiments support the view, put forward earlier, that this low friction is due to a localized surface melting produced by frictional heating. Measurements are made on a variety of surfaces including metals, synthetic polymers and waxes. The contact angle which water makes with the surface is important, and there is evidence that this can decrease during sliding. In general, the solids with a high contact angle give a lower friction. The behaviour is also influenced by the relative hardness of ice and of the ski surface at the temperature of sliding. Polytetrafluoroethylene gives a very low friction on snow and ice under all conditions.