The initial kinetic energy of the car is

Then, the velocity of the car is decreased by half:

so, the new kinetic energy is

So, the new kinetic energy is 1/4 of the initial kinetic energy of the car. Numerically:
As per Bernuolli's Theorem total energy per unit mass is given as

now from above equation




now by above equation


Part B)
Now energy per unit weight


