Which of the following measures how quickly something is speeding up?

Acceleration is defined as the rate at which an object changes its velocity over time. When an object speeds up, it experiences positive acceleration. This measurement is crucial in physics because it not only indicates how fast an object's speed is increasing but also provides insights into the forces acting upon it.

In contrast to acceleration, velocity refers to the speed of an object in a specific direction, making it a measure of both speed and direction, but not of how that speed is changing. Displacement represents the change in position of an object, while deceleration specifically refers to negative acceleration, which occurs when an object slows down. Therefore, acceleration is the correct response for measuring how quickly something is speeding up.