VIDEO: The difference between normal force and weight
Weight force and normal force - the physics for it
- The weight force is the force with which a body or object is attracted to the earth. Some use the terms "gravity" or "gravity" instead of weight. Of course, the moon also exerts a weight or gravity on the body, but this is significantly smaller.
- The weight of a body can be easily calculated. It only depends on the mass m (in kg; in everyday life also called weight) and the acceleration due to gravity g 0 9.81 m / s² from: G = m * g (in the unit Newton "N").
- The normal force is figuratively speaking the force with which a body presses on its base. The normal force is always perpendicular to this base - hence the name.
- If the base is parallel to the earth's surface (i.e. perpendicular to the earth's radius), then the two forces are the same in terms of both direction and magnitude.
- The normal force also plays a role in friction, because part of this force (static friction) has to be overcome, for example, when starting and driving (sliding friction).
Inclined plane - the formulas physically examined
An inclined plane can be a steep uphill stretch, but also the thread ...
The incline makes a difference
What happens, however, if the surface on which the object is located and the surface of the earth do not coincide or are not parallel? The best example that there is a difference between normal force and weight is the inclined plane.
- For example, if a car is pulled along a ramp onto a tow truck, then the crane or the winch does not use the entire weight G of the car (that is the point of an inclined plane: to save forces). Depending on the steepness of the incline, the so-called. Downhill force H much smaller than G (precisely: H = G * sin (alpha) = G * s / h, where alpha is the angle of inclination of the inclined plane and s is the length or h is the height of the plane.
- However, here the normal force, i.e. the force with which the car presses on the inclined ramp, is also much smaller than the weight force. It is usually referred to as the tracking force. A = G applies * cos (alpha).
- In the extreme case, the difference between the two forces is astonishingly noticeable: Is that inclined plane a vertical, i.e. alpha = 90 °, then there is no longer any normal force (cos (90 °) = 0).
- By the way: If the normal force is greater than the resistance of the ramp, it will crack! With "weak" ramps there is a big one angle cheap; however, the downhill force that the crane has to generate is then also greater.
One more remark for those interested in physics: In fact, the weight on the inclined plane splits vectorially (i.e. not in terms of amount) in the two forces discussed - in many books one can find the parallelogram of forces from which the named Relationships or Formulas.
