Which physical quantity is defined as the rate of change of velocity?

Acceleration is defined as the rate of change of velocity. It measures how quickly an object's velocity changes over time, which can include increases or decreases in speed and changes in direction. Mathematically, acceleration is calculated by taking the change in velocity and dividing it by the time interval over which that change occurs. This relationship can be expressed with the formula:

[ a = \frac{\Delta v}{\Delta t} ]

where ( a ) is the acceleration, ( \Delta v ) is the change in velocity, and ( \Delta t ) is the change in time. Understanding acceleration is crucial in physics, as it connects directly to concepts of motion and dynamics, influencing how objects respond to forces acting upon them.

The other choices represent different physical concepts: force refers to any interaction that changes the motion of an object, momentum is the product of an object's mass and its velocity, and velocity itself is simply the speed of an object in a specific direction. Each of these quantities has its own unique definition and role in the study of physics, distinct from what acceleration describes.