What type of force is exerted only when two objects are in contact?

The correct answer is contact force, which specifically refers to the forces that occur between two objects when they are physically touching each other. Contact forces arise from the interactions at the surface level, such as the push or pull that one object exerts on another.

Frictional force is a specific type of contact force that opposes the motion of two surfaces sliding past each other, but it is only one example of contact forces, which encompass various other interactions as well, such as tension in a string, normal force from a surface, and applied force. Gravitational force, on the other hand, acts at a distance and does not require contact between the objects involved; it pulls objects toward one another based on their masses. Similarly, magnetic force can also act at a distance without direct contact, influenced by charged particles. Thus, the defining characteristic of contact force is that it requires physical interaction between two or more bodies.