Key Idea.
Section 1
Changes in Motion Reveal Forces
Objects can be still or moving. When a still object starts to move, or a moving object stops, this is called a change in motion. A push or a pull is needed to cause this change.
Therefore, any change in motion—such as a swing starting to move or a rolling ball slowing to a stop—is observable evidence that a force has acted on the object.
Expand to review the lesson summary and core properties.
Section 1
Changes in Motion Reveal Forces
Objects can be still or moving. When a still object starts to move, or a moving object stops, this is called a change in motion. A push or a pull is needed to cause this change.
Therefore, any change in motion—such as a swing starting to move or a rolling ball slowing to a stop—is observable evidence that a force has acted on the object.