Two questions I had: 1. How is the force of friction of the tires pointed inwards to cause centripetal acceleration? If the tire is rotated when trying to turn, the car is still traveling with a velocity perpendicular to the circle and force of friction would still be counteracting the direction of movement? 2. How can gravity = centripetal acceleration at the top of loop de loop? They are pointed in same direction downward? Also i have been told that normal force is zero when centripetal acceleration = gravity. If normal force is zero, the car wouldn’t be in contact with the road then and would fall? Second, I was told that normal force increases as centripetal acceleration increases. However, isn’t normal force pointing downward toward the center counteracting the car pushing on the road upward? But also if gravity is pointing downward, how is the car even exerting force on the road upward? To me it seems all the forces are pointed in the downward direction at the top of the loop.