Answer:
1. The force of the car engine.
Explanation:
We shall see the effect and role played by each force, one by one, as follows:
1. The force of car engine:
The engine produces a force through combustion that is converted to mechanical work through the shaft. This work is then transmitted to the wheels of the car that cause the motion in the car and increase its kinetic energy.
2. Air Resistance:
It is the opposing force of air that tries to reduce the motion of the car and as a result, reduce its kinetic energy.
3. Frictional Force between road and tire:
It is also the opposing force of air that tries to reduce the motion of the car and as a result, reduce its kinetic energy.
4. Gravity:
Gravity pulls everything towards the center of Earth so it does not have much significant role in horizontal motion like this.
Hence, the force of the car engine did the work that increased the car's kinetic energy.
