Hi everyone, good day. when a car is moving (accelerating), what are the forces that actually acted on the car? Is it possible to draw a free body diagram to illustrate the idea? (please draw one for me, i really need this in order to understand) I am having problem in relating how the engine torque causing the car to move forward. i mean i can totally understand how engine convert chemical energy in petroleum to rotating output shaft, and how output shaft goes through gearing to the wheel (i understand the physical mechanism). but i failed to draw a free body diagram to analyze the system. Also, i am quite confuse in the direction of friction acting on the car wheels. Say, the car is front wheel driven by engine, i heard people saying the friction force is the same direction as the car's forward motion on the front wheel (driven by engine), while is in the opposite direction with the car's forward motion on the back wheel (non driven wheel). is this true? if it is, can you please explain to me why it is so? Thanks a lot for you reply!