A box contains 105 molecules. The average kinetic energy of each molecule is 0.5*10-6J. With respect to an observer at rest the box, having a mass of 1kg, is moving with a velocity of 2m/s. What is the value of kinetic energy that will contribute to the internal energy?

Heat is the energy in transit whenever temperature differences exist. The internal energy is equal to the sum of internal kinetic energy due to molecular motion and internal potential energy due to molecular attractive forces. A hot body has more internal energy than an identical cold body.