(falling-weight test) n. A test for the impact resistance of rigid plastic sheets or parts. ASTM D 3029 describes two methods, F and G. In F, a weight with a hemispherical nose falls through a tube to strike the specimen, and G (for which the Gardner Impact Tester is approved), in which the falling weight hits a round-nose striker resting on the specimen. Either the weight or the height of drop may be varied, the former being recommended because of the sensitivity of most plastics to the velocity of impact (determined by height). Several tests on new specimens may be made at each impact-energy level (height × weight), and the fraction of breaks at each level is noted. This procedure efficiently provides information on both the mean energy to break and the standard deviation. Where the mean is of greatest interest, the up-and-down method provides a good estimate with less testing (Paul N. Gardner Co. Inc., 316 N. E. Fifth Street, Pompano Beach, FL, www.gardco.com).