clara2018 23/04/2015 Ec = 1/2 x m x v²9000 = 1/2 x m x 30²9000 = 1/2 x 900 x m9000 = 450 x m9000 / 450 = mm = 20 kg
clara2018
Ec = 1/2 x m x v²
9000 = 1/2 x m x 30²
9000 = 1/2 x 900 x m
9000 = 450 x m
9000 / 450 = m
m = 20 kg