Chapter 5, Problem 5.57P

A sensitive material is to be contained within a glovebox. Codes require that the transparent panels that make up the walls of the glovebox withstand the impact of a 22-kg mass falling at 8 m/s. An impact test is performed where the 22 kg mass is dropped a known variable height onto a panel. The mass motion is sensed by photocells from which an impact velocity is estimated. The mean kinetic energy for failure was 717 N-m, with a standard deviation of 60.7 N-m based on 61 failures. The systematic uncertainty in mass is 0.001 kg (95%). The velocity at impact is 8 m/s. with a systematic uncertainty in velocity estimated as 0.27 m/s (95%). Estimate the combined standard uncertainty and the expanded uncertainty at 95% in the kinetic energy for failure. Assume a normal distribution of errors.