Which scenario demonstrates acceleration due to a change in direction, even if speed is constant?

• A. A car going around a curve in the road at a constant speed
• B. A car driving in a straight line that changes speed from 20 mph to 40 mph
• C. A car driving in a straight line at a constant speed
• D. A car going around a curve that changes speed from 20 mph to 40 mph

Answer: (A)

Acceleration is a change in velocity, which means a change in either speed or direction (or both). When a car moves around a curve at constant speed, its direction is continually changing while the magnitude of velocity stays the same. That change in direction means the velocity is changing, so the car experiences acceleration toward the curve’s center—centripetal acceleration. The other scenarios either change speed in a straight line, have constant velocity with no direction change, or involve both speed and direction changes, so they don’t show acceleration caused purely by a change in direction with constant speed.