Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: Acceleration is a measure of the change in velocity of a moving object. It shows how quickly velocity changes. Acceleration may reflect a change in speed, a change in direction, or both. Because acceleration includes both a size (speed) and direction, it is a vector. Answer: acceleration
What is the measure of change in velocity of a moving object?