What force acts in opposition to an object moving along a surface?

Friction is the force that acts in opposition to an object moving along a surface. When an object moves, frictional forces arise between the object's surface and the surface on which it travels. This force works to resist the motion and can slow down or stop the object.

For example, if you push a box across a floor, friction between the box and the floor will oppose your push, making it harder to move the box compared to if there were no frictional force at play. The amount of friction depends on various factors, including the materials of both surfaces and how much force is pressing them together.

The other forces mentioned do not directly oppose motion in the same context as friction. Gravity acts vertically downwards and influences the weight of the object but does not resist horizontal motion directly. Inertia is a property of matter that describes an object's tendency to resist changes in its state of motion, but it does not exert a force itself. Momentum is a measurement of the motion of an object that involves both its mass and velocity, but it does not represent a force that opposes motion.