If a car has a kinetic energy of 400 J at 20m/s what. is the cars kinetic energy in kJ at a speed of 5 m/s

Kinetic energy is an expression of the fact that a moving object can do work on anything it hits; it quantifies the amount of work the object could do as a result of its motion. It can be calculated as:

KE = mv^2 / 2

We calculate the problem as follows:

KE = mv^2 / 2

400 = m (20) ^2 / 2

m = 2 kg