The initial kinetic energy of the car is
[tex]E_1 = \frac{1}{2}mv_1^2 = 1.9 \cdot 10^3 J[/tex]
Then, the velocity of the car is decreased by half: [tex]v_2 = \frac{v_1}{2} [/tex]
so, the new kinetic energy is
[tex]E_2 = \frac{1}{2}mv_2 ^2 = \frac{1}{2} m ( \frac{v_1}{2} )^2= \frac{1}{2}m \frac{v_1^2}{4}= \frac{E_1}{4} [/tex]
So, the new kinetic energy is 1/4 of the initial kinetic energy of the car. Numerically:
[tex]E_2 = \frac{1.9 \cdot 10^3 J}{4}=475 J [/tex]
