<u>Answer:</u>
<em>The average speed of the car is 66.9 km/h</em>
<u>Explanation:</u>
Here distance covered with the speed <em>57 km/h=7 km </em>
distance covered with the speed of <em>81 km/h=7 km</em>
<em>Average speed is equal to the ratio of total distance to the total time.
</em>
<em>total distance= 7 + 7= 14 km </em>
<em>
</em>
<em>time taken to cover the first 7 km= 7/57 h </em>
<em>time taken to cover the second part of the journey = 7/81 h
</em>
<em>average speed = 
</em>
<u><em>Shortcut:
</em></u>
<em>When equal distances are covered with different speeds average speed=2 ab/(a+b) where a and b are the variable speeds in the phases.
</em>
Answer:
0 J
Explanation:
Kinetic energy is defined as:
KE = 1/2 m v²
where m is mass and v is velocity.
The car starts at rest, so it has zero velocity. Therefore, its initial kinetic energy is 0 J.
Homogeneity and isotropy, On large enough scales, the Universe looks pretty much the same in all directions. The big bang theory is based on two assumptions: the first is centered around Einstein's general theory of relativity, which accurately describes gravity and the interactions of matter; and the second, also known as the cosmological principle, asserts that the universe is homogeneous and isotropic on a large enough scale.
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