I read an example in my physics book and was not satisfied with that.
Suppose there is a car initially at rest. If the car accelerates then my book says that it is the friction force only which caused this acceleration since it is the only external force acting on the car. But I was not satisfied with that.
What I think is that the motion of the car was the result of both friction as well as the force exerted by the engine on the wheels. If there was no friction then the wheels would rotate only and will not move forward. But what if there was no engine and no external force was given except friction. The car would not move in both the cases. Doesn't it mean that for acceleration both internal as well as external force is needed?
If it is correct then why don't we count the internal force?
If I am wrong, then correct me.