Contact force

The distinction between contact and non-contact forces depends on the interacting objects, not on whether either object is moving. Contact forces act when objects physically touch. Friction acts between touching surfaces and opposes their movement, or attempted movement, past each other.

The force of Earth’s gravity on the ball is its weight. This is a gravitational interaction, not a contact force from the ground.

The book presses down on the table, while the table pushes up on the book with a normal contact force. Here, “normal” means perpendicular to the surface.