Which statement describes a push or pull changing motion?

• A. Mass
• B. Velocity
• C. Energy
• D. Force

Answer: (D)

A push or pull is a force, and it’s the force that changes how an object moves. When you apply a push or pull and there isn’t an equal and opposite force balancing it, you create a net force. This net force makes the object's velocity change—that is, it accelerates according to F = ma. Mass relates to how hard it is to change motion (inertia), so for a given force a larger mass changes velocity less, and a smaller mass changes velocity more. Velocity describes how fast and in what direction something is already moving, not what causes the change. Energy is a property tied to motion or work done, but it isn’t the direct cause of changing motion. So the statement that best describes a push or pull changing motion is Force.