What is the definition of a push or a pull in physics?

In physics, a push or a pull is defined as a force. Force is a vector quantity that causes an object to undergo a change in motion, which can include starting to move, stopping, or changing direction. This concept is fundamental in understanding interactions between objects; for example, when you push a stationary object, the force applied initiates movement, and when you pull an object, the force acts to draw it closer to you.

The other choices represent different physical quantities that, while related to motion and forces, do not directly define a push or a pull. Velocity refers to the speed and direction of an object's movement, acceleration indicates a change in velocity, and momentum is the product of an object's mass and its velocity, which describes motion but not the action initiating that motion. Thus, force is the correct term to describe a push or a pull.