Final answer:
On a straight road, slight adjustments are made to maintain vehicle position in the lane. On a perfectly banked curve, you won't feel thrown sideways because the force is downwards through the car seat. The centripetal force stretching the string on a circular path comes from the string's tension as per Newton's third law.
Step-by-step explanation:
On a straight road, the correct steering adjustments to make are slight adjustments to maintain the vehicle's position (Option 2). This is necessary to keep the vehicle within the lane and compensate for any minor external factors such as road irregularities or wind that might cause the vehicle to drift. Now, when you negotiate a curve that is ideally banked for your car's speed, you should not feel yourself thrown to either side because the banking of the turn and your speed are matched in such a way that the net force is directed downward through the car seat, thus avoiding any lateral centrifugal force that would push you against the side of the car.
If a mass is moving in a circular path on a frictionless table, it is the centripetal force that stretches the string attaching the mass to the nail. This force originates from the tension in the string, as every action has an equal and opposite reaction, as per Newton's third law. The physical origin of this force is the mass's inertia, which resists change in motion, and the string's tension that redirects the mass towards the center, maintaining circular motion.