Tangential acceleration affects velocity magnitude, not direction. Which option best reflects this statement?

• A. It changes the magnitude of velocity.
• B. It changes the direction of velocity.
• C. It changes the magnitude of the centripetal acceleration.
• D. It changes nothing about velocity.

Answer: (A)

Tangential acceleration is the component of acceleration along the path of motion, and it directly changes how fast you’re moving along that path. It equals the rate of change of speed: a_t = dv/dt. Because velocity has a magnitude and a direction, changing the speed alters the magnitude of velocity, while the direction is controlled by the radial (centripetal) component that pulls the motion toward the center of curvature. So when tangential acceleration is present, you speed up or slow down, but you don’t instantly redirect the motion—the direction remains governed by the centripetal effect. That’s why the best statement is that tangential acceleration changes the magnitude of velocity. The other possibilities either ignore that speed-change effect, misattribute direction change to tangential components, or focus on a secondary consequence (centripetal acceleration) rather than the primary, direct impact on velocity magnitude.