An assumed ideal (spherical) particle having the same density as water, falling in still air, used for calculating theoretical values for terminal velocity
John Gilbertson (Ed.), Health and Safety Sound Bites, Category: Agriculture and Industry, Health and Safety Sound, County, ENCYCLO Online Encyclopedia, from Safety & Health Practitioner SHP (The Official Magazine of The Institution of Occupational Safety and Health (IOSH), United Business Media Limited, London, UK 2007. http://www.encyclo.co.uk/local/20474&page=4, (OSH - Brit) {117}