The car is traveling at v=12m/s. Kinetic energy is given by this formula:
[tex]E_k=\frac{mv^2}{2}[/tex]
We can see that if the kinetic energy depends on the speed quadratically. This means that if you want to increase the kinetic energy x times you would have to increase speed [tex] \sqrt{x} [/tex] times. We conclude from this that car would have to go:
[tex]v'=\sqrt2v=\sqrt2\cdot 12=16.97\frac{m}{s}[/tex]
