A car has the kinetic energy of 432000 Joules when traveling at a speed of 42 m/s. What is its mass? (Kg) I know that K.E. = (1/2)(Mass)(Velocity squared) So the equation reads 432000 = (1/2)(42 squared)(M) I got an answer of 150 but my online program told me it was wrong. Help? Do I need to convert units somewhere?