Which of the following best describes $\mathrm{negative} \mathrm{acceleration}$?

• A. It means the object is moving at a constant speed in a straight line.
• B. It refers to an object that is stationary and not experiencing any change in $\mathrm{velocity}$.
• C. It occurs when an object's $\mathrm{velocity}$ decreases over time, meaning the $\mathrm{acceleration}$ vector points opposite to the direction of motion.
• D. It occurs when an object's $\mathrm{velocity}$ increases over time, meaning the $\mathrm{acceleration}$ vector points in the same direction as the motion.

Answer: (C)

Verified step by step guidance

1. Understand that acceleration is the rate of change of velocity with respect to time, expressed as \(\vec{a} = \frac{d\vec{v}}{dt}\).
2. Recognize that 'negative acceleration' means the acceleration vector points in the opposite direction to the velocity vector.
3. Recall that when acceleration is opposite to velocity, the object's speed decreases over time, which is often called deceleration.
4. Note that constant speed in a straight line means zero acceleration, and a stationary object with no change in velocity also has zero acceleration.
5. Conclude that negative acceleration best describes a situation where the object's velocity decreases over time because acceleration opposes the direction of motion.