Hi! :) I'm confused about the direction of the friction vector when we decelerate and when we turn. I've memorized the directions (if I decelerate going east, friction is aimed west; if I am in a flat circle and going around it, friction points to the middle), but they don't exactly make sense to me. I do know that friction opposes relative motion. Issue 1: So, there is a car accelerating to the east. The tires are spinning clockwise. Basically, the tire is pushing LEFT against the road. Friction opposes this and thus the friction vector points RIGHT (towards the east). I understand that pretty well. But when we decelerate (say slowing down while still moving east), the friction vector now points to the left? So the same car is decelerating to the east. The tires are still spinning clockwise. The tires are now pushing RIGHT (somehow? :uhh:). Friction opposes this and thus the friction vector now points LEFT (towards the west...somehow? :uhh:). I don't understand what motion friction is opposing when the car is decelerating? In the acceleration one, it is opposing the force of the tires pushing left. But in the deceleration one, isn't that the same motion? And thus friction seems to point forward? Issue 2 So, friction allows cars to turn and its vector points towards the center of the circle (the circle they would "draw" if they went all the way around). But, if I apply the "wheels push against the road-and-friction-opposes-that", then it seems as if the friction force should point the same direction the wheels are pointing. Like here: http://img855.imageshack.us/img855/2621/57fba08c2966484b9cf8885.png [Broken] But that isn't right at all. Why does this "wheels push against the road-and-friction-opposes-that" rule only work for the car accelerating forward? If that isn't a good way to "visualize" this or wrap my head around it (ostensibly so), any suggestions? I have heard that if the net force is friction, it will be in the same direction as acceleration (through Newton's 2nd Law). But, I don't know how to say this, but that sounds like the result and not the steps in understanding it.