A woman standing beside a road sees a car accelerate from rest to \(30 \mathrm{~m} / \mathrm{s}\). Describe the car's motion as seen by the driver of a truck traveling in the same direction as the car at a constant \(30 \mathrm{~m} / \mathrm{s}\). What if the truck is moving in the opposite direction? Is the direction of acceleration of the car affected by the (constant) velocity of the truck driver relative to Earth?