Find the mass in kg, if the energy is 7.81 x10^13

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

Gordon is going for a run through the park, but it is cold outside. the low outside temperature could affect his personal safety.

Since the energy was not raising the temperature of the water during these segments, what was the energy used to do instead? your answer must include an explanation of what is happening to the molecules.