Two friends, joe and sam, go to the gym together to strength train. they decide to start off with an exercise called flat bench press. lying flat on a bench with his arms in an extended position, each friend slowly lowers (to his chest) and then raises a barbell back to the starting position. they start off by using a 31.5 kg barbell. joe is taller than sam, which means joe's arms are 67.2 cm long whereas sam's are 59.2 cm . calculate the work done by joe - wjoe when he raises the barbell to finish one repetition. the acceleration due to gravity is 9.81 m/s2 .