Explanation:

Friction is the force that works in the opposite direction of movement of an object in contact with a surface. When an object is in contact with a surface and there is relative motion or an attempt of motion between the object and the surface, friction comes into play. It acts to oppose or resist the motion or the attempted motion.

Friction:
Friction is a force that occurs when two surfaces come into contact with each other. It acts to oppose the relative motion or tendency of motion between the two surfaces. Friction is caused by the irregularities or roughness of the surfaces in contact. The rougher the surfaces, the greater the friction.

Opposite Direction of Movement:
When an object is moving or attempting to move in a certain direction, the frictional force acts in the opposite direction. For example, if you try to push a box to the right, the frictional force will act to the left, opposing your motion. This is because the frictional force is trying to prevent the box from sliding or moving in the direction you are pushing.

Gravity, Push, and Pull:
Gravity is the force that attracts objects towards each other. It acts vertically downwards, pulling objects towards the center of the Earth. It is not the force that works in the opposite direction of movement of an object in contact with a surface.

Push and pull are forces that can cause movement. Pushing is applying force in a specific direction away from oneself, while pulling is applying force in a specific direction towards oneself. However, these forces are not specifically working in the opposite direction of movement, as they can also be applied in the same direction as the intended motion.

Conclusion:
The force that works in the opposite direction of movement of an object in contact with a surface is friction. Friction opposes the motion or attempted motion between two surfaces in contact and acts in the opposite direction of the applied force.