Answer: Within any frame of reference that is accelerating
Special relativity was proposed on 1905 by Einstein, who developed his theory based on the following two postulates:
1. <em>The laws of physics are the same in all inertial systems. There is no preferential system.
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2. <em>The speed of light in vacuum has the same value for all inertial systems.
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Focusing on the first postulate, it can be affirmed that <u>any measurement on a body is made with reference to the system in which it is being measured</u>.
Now, taking into account that an inertial reference system is the one that complies with the principle of inertia:
<em>"For a body to have acceleration, an external force must act on it."</em>
The correct answer is
Within any frame of reference that is accelerating
Based on your question where a car leaves skid marks 85m long on the highway nad getting to stop. The deceleration of the car is 3m/s^2 to estimate the speed of the car just before braking first is to analyze the problem then apply the necessary formulas. the possible answer is 510m/s
The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon
So I believe it’s 6 hope this helps if not reply back