Why is slowing down considered $acceleration$ in physics?

• A. Because $acceleration$ refers to any change in $velocity$, including a decrease in speed, which is called negative $acceleration$ or deceleration.
• B. Because $acceleration$ is always positive, so slowing down cannot be considered $acceleration$.
• C. Because $acceleration$ is defined as the rate of change of position, so slowing down does not affect $acceleration$.
• D. Because $acceleration$ only occurs when an object speeds up, so slowing down is not $acceleration$.

Answer: (A)

Verified step by step guidance

1. Recall the definition of acceleration in physics: acceleration is the rate of change of velocity with respect to time, expressed as \(\\mathbf{a} = \\frac{d\\mathbf{v}}{dt}\).
2. Understand that velocity is a vector quantity, meaning it has both magnitude (speed) and direction. Any change in either magnitude or direction constitutes a change in velocity.
3. Recognize that slowing down means the magnitude of velocity (speed) is decreasing over time, which is a change in velocity.
4. Since acceleration measures any change in velocity, a decrease in speed corresponds to acceleration in the direction opposite to the velocity vector, often called negative acceleration or deceleration.
5. Therefore, slowing down is considered acceleration because acceleration includes both increases and decreases in velocity, not just speeding up.