Answer:
The car’s kinetic energy at the bottom is 4 times its kinetic energy at the top. The car has 1800 joules of kinetic energy at the bottom of the hill.
Step-by-step explanation:
The kinetic energy of the car is given by:

where m is the mass of the car and v its speed.
First of all, we see that the kinetic energy is proportional to the square of the speed: since the speed of the car at the bottom of the hill is twice the speed at the top of the hill, then the new kinetic energy must be
times the kinetic energy at the top.
We can explicitely calculate it by using the formula.
At the top of the hill:

At the bottom of the hill, the speed has doubled, so it is 6 m/s; therefore, the kinetic energy is
