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The first statement is true only if one does not measure exactly. If you were infinitely can accurately measure could already notice a relativistic effect at car speeds. But this is so enormously small that one can neglect it in good conscience and therefore v (tot) = v (1) + v (2) an almost perfect approximation achieved to reality.
A speed trap would not notice it.
Rates do not add up as one might think à la: v1 + v2 = v3, which applies only approximated at low speeds. A total velocity (or apparent speed when two objects move toward each other) will never be higher than c.
If you want to know more, it is the relativistic addition theorem for velocities ( http: //de.wikipedia.org/wiki/Relativistisches_Additionstheorem_f%C3%BCr_Geschwin ... )
You have to remember that the normal velocity addition applies only to Galileo transformations, ie for system with speeds significantly less than the speed of light. This means that the simple Geschwindigkeitsverktoraddition only represents a very good approximation for small Geschwindikeiten.
Relativistic and thus exactly be considered you must have recourse to the Lorentz transformation.
http: //de.wikipedia.org/w/index.php title = Relativistisches_Additionstheorem_f% C3 ...?
This is then a little more complicated. If you can see in this case v << c do you work as a limit comes out the classical addition.
The speed is not greater than c. You also need to have in mind that change due to the length contraction, the extent of the body and of the system.
It depends on the reference system.
You've expressed all too vague.
You move 2 cars A and B, resulting in a reference frame of reference (eg road) each 100km / h. You move toward itself, that is measured in the reference frame of reference distance becomes smaller with 200km / h. If you as a reference system now but the car A take, then STANDING in this reference system, the car A, the road moves at 100km / h and the car B with 200km / h.
You can have a frame of reference (eg "laboratory", "light source"), in the moving apart the two photons A and B at 2X speed of light. But it is impossible to find a reference system (as in cars), in which a single object, ie For example, photon A moves with more than the speed of light.
Remember, the relative speeds have nothing directly to do with physics, as not subject to the absolute physical laws.
When move the car with 100km / h each other, then still drives each with 100km / h, has the same air resistance, the same engine power needs, etc. than when driving alone. Driving each other to then meet up in half the time as when one of the cars would be and the other 200km / h would go. but do not! That it comes that meet two people, then this happens with two cars in half the time, but that does not change the physics of the cars.
Also in the photon that is so, also which are not interdependent. The then meet together in half the time, but every fly for still the speed of light.
The speed of light is the maximum possible speed. Anything beyond that is rounded to the speed of light.