The kinetic energy (K.E.) of a body can be calculated using the formula:
K.E. = (1/2) * mass * velocity^2
Given that the mass of the body is 12 kg and the velocity is 400 m/s, we can substitute these values into the formula:
K.E. = (1/2) * 12 kg * (400 m/s)^2
K.E. = 0.5 * 12 kg * (160,000 m^2/s^2)
K.E. = 6 kg * 160,000 m^2/s^2
K.E. = 960,000 joules (J)
Therefore, the kinetic energy of the body is 960,000 joules.