Final answer:
The correct description of a car with a velocity of +3 m/s is that it changes its position by 3 meters to the right every second, as velocity here indicates the direction (to the right) along with the speed of the car.
Step-by-step explanation:
The correct statement that best describes the motion of a car traveling at a velocity of +3 m/s is (a) The car's position changes by 3 meters to the right every second. This statement is true because a positive velocity indicates that the motion is in the positive direction, which is conventionally to the right. The 'right' refers to the direction along the positive side of the axis being used to describe the motion, which is a standard convention in physics.
The velocity of an object is its speed in a given direction. Here, the speed of the car is 3 meters per second (m/s), and the positive sign indicates the direction is to the right. This does not imply any change in velocity, but instead a constant velocity, which means there is no acceleration involved – the car is not speeding up or slowing down, so options (c) and (d) are incorrect.
As for options (b), the negative sign would indicate the object is moving to the left, which is not the case given the positive sign of the velocity. It's important to understand that velocity is a vector quantity and includes both magnitude (speed) and direction. Hence, the provided velocity of +3 m/s defines not just how fast the car is going, but also the direction.