Which car is accelerating?$a$

• A. A car parked in a parking lot
• B. A car increasing its speed while driving forward ($v\uparrow$)
• C. A car driving at a constant speed around a circular track ($v=\mathrm{const}$, circular motion)
• D. A car moving at a constant speed in a straight line ($v=\mathrm{const}$, straight line)

Answer: (B)

Verified step by step guidance

1. Recall the definition of acceleration: acceleration occurs when there is a change in the velocity of an object. Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.
2. Analyze each scenario: - A parked car has zero velocity and no change in velocity, so its acceleration is zero. - A car increasing its speed while driving forward has a change in the magnitude of velocity, so it is accelerating. - A car moving at constant speed around a circular track has a constant speed but its direction is continuously changing, which means its velocity is changing and it is accelerating (centripetal acceleration). - A car moving at constant speed in a straight line has constant velocity, so no acceleration.
3. Understand that acceleration can be due to changes in speed or direction (or both). Therefore, both increasing speed and changing direction imply acceleration.
4. Identify which option explicitly mentions increasing speed, which is a clear case of acceleration.
5. Conclude that the car increasing its speed while driving forward is accelerating because its velocity magnitude is changing.