* Normal force: The force exerted by a surface on an object in contact with it perpendicular to the surface.

* Frictional force: The force that opposes the motion of an object in contact with a surface.

* Tension force: The force exerted by a string, rope, or cable on an object attached to it.

* Compression force: The force that acts to compress or shorten an object.

* Elastic force: The force exerted by an elastic object, such as a spring or rubber band, when it is stretched or compressed.

All of these forces require contact between two objects in order to have an effect. For example, the normal force is the force that the ground exerts on your feet when you are standing on it. The frictional force is the force that opposes the motion of your car when you are driving it. The tension force is the force that the rope exerts on your sled when you are pulling it. The compression force is the force that acts to compress or shorten your spring when you are sitting on it. The elastic force is the force that the rubber band exerts on your finger when you are stretching it.