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newton's third law. it states that for any force, there is an equal and opposite force. There is a force of gravity pushing down on everything (on Earth), yet we don't fall through the ground. Just as we push down on the ground with our weight due to gravity, the ground pushes back on us with an equal force. This keeps us in equilibrium and we remain motionless.
I think this is the best image to explain it: F_N is the normal force F_G the gravitation http://upload.wikimedia.org/wikipedia/de/0/04/Schiefe_ebene_4_.png
"Normal" is a mathematical term meaning perpendicular. A normal force is a force in a direction perpendicular to the surface at a particular location. The normal force can be a component of a force - that is you can break a force up into a part (vector component) perpendicular to a surface and a part (vector component) parallel to a surface - and concentrate attention on one component or the other. (The only requirement is that those vector components add up to the give back original force.) Normal components of forces are often of interest because they are related to frictional forces.
I had the same question recently. I like Stan's answer, and have a follow-up question: In the simple type of problem where we assess the motion of an object on an inclined plane, we draw the normal force vector perpendicular to the plane, as expected. My question is this: does that vector represent the actual contact force between the object and the plane (i.e. is the plane 'pushing' the object in that direction), or simply one component vector of the contact force? (I hope this question makes sense!)
I think of it as a component of the contact (surface) force. In some situations the surface may be able supply forces in additional directions. For example, if the inclined plane is frictionless, the surface can only supply a force in the normal direction (no friction along the surface to cancel out the component of the weight (gravitational force) down the slope), so the contact force is the normal force. But for rough (frictional) surfaces the surface will be able to supply a force component counter to the component of the gravitational force down the slope, and in this case, the normal force is just a component of the contact force (the other component would be the frictional force on the object supplied by the surface).
normal force is actually the vertical component of contact force.contact force is result due to the electrostatic force of attraction between bodies in contact in microscopic level.the other component of contact force i.e is horizontal component is frictional force.
normal force is just a name given to the force if there is contact between two bodies. i think it is better to use the name contact force.
"Normal" tells you the direction... "contact" doesn't
Actually when two bodies are in contact they have a common surface,all the forces along the normal to that common surface are normal forces