If asked to exert a force on an object, you will most probably either push or pull the object. Either results in what is called a contact force , referring to the contact between you and the object while the force is being exerted. Our intuitive feel of forces is not always correct. For instance, you would rather experience a force exerted through the palm of a hand than a force of equal magnitude exerted through the tip of a needle. Non-contact forces are forces acting at a distance without any direct contact.
Gravity is an example of a non-contact force.
The weak and strong forces are responsible for holding nuclei together. In this experiment, you will investigate the relationship between force and acceleration by assuming that Newton s Second Law of Motion is correct, and then testing the logical consequences of this hypothesis. If the predictions of the hypothesis can be shown to be valid, then we gain a certain amount of confidence that the second law is the correct description of the relationship between force and acceleration. A glider sits on an airtrack without moving. Draw a free body diagram indicating all of the forces acting on the glider.