Which statement describes acceleration on a straight path where speed changes?

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

Answer: (A)

Acceleration is the rate at which velocity changes. On a straight path, the direction stays the same, so any acceleration comes from a change in speed. Increasing speed from 20 mph to 40 mph while traveling in a straight line means the velocity is increasing in magnitude, which is acceleration. The other scenarios either involve turning (a curved path) where direction changes and velocity changes even if speed might be constant, or a straight path with constant speed where velocity doesn’t change at all. So the straight-line change in speed from 20 mph to 40 mph best describes acceleration on a straight path.