This part of IS0 7765 specifies methods for the determination of the energy that causes plastics film and sheet less than I mm in thickness to fail under specified conditions of impact of a free-falling dart from a specified height that would result in failure of 50 % of the specimens tested. 1.2 Two methods of test are described. 1.2.1 Method A employs a dart with a 38 mm + I mm diameter hemispherical head dropped from a height of 066 m + 0,OI m. This method may be used for materials whose impact resistance requires masses of about 0,05 kg to about 2 kg to fracture them. 1.2.2 Method B employs a dart with a 50 mm + I mm diameter hemispherical head dropped from a height of I ,50 m + 0,OI m. Its range of applicability is from about 0,3 kg to about 2 kg. I.3 The measurement technique is the staircase method. A uniform missile mass increment is employed during testing and the missile weight is decreased or increased by the uniform increment after test of each specimen, depending upon the result (failure or no failure) observed for the specimen.