South Carolina READY 4th Grade Science Practice Test

Friction is the force that opposes motion between two surfaces that are in contact with each other. When one surface slides against another, friction acts to resist that sliding motion. This force is caused by the interactions between the molecules on the surfaces.

For example, when you push a book across a table, friction works against the motion of the book. It is this resistance that makes it harder to move the book smoothly, and if the push is not strong enough to overcome the friction, the book will remain at rest.

Understanding friction is essential in many real-world applications, such as driving a car, walking, or even playing sports, where it plays a critical role in how objects move or stop.