<h2>Answer:</h2>
<h2>Explanation:</h2>
First, let's refer to the distance formula:
, where d is distance, v is velocity or speed and t is time.
Now, let's find the distance covered by each individual speed that the car had:
<h3>1. Speed 1.</h3>
In order to use the formula, we need to convert minutes into hours since the speed is given in km/h.
21.1 min/60= 0.35 h.
Now, apply the distance formula.
d=(0.35h)*(86.8km/h)= 30.38 km.
<h3>2. Speed 2.</h3>
Convert minutes to hours again and do the same calculations.
10.6min/60=0.18h
d=(0.18h)*(106km/h)= 19.08 km.
<h3>3. Speed 3.</h3>
36.5min/60= 0.61h
d=(0.61h)*(30.9km/h)= 18.85 km.
<h3>4. Obtain the total distance.</h3>
The total distance must be given by the addition of all individual distances traveled by the car on each speed:
Total distance= 30.38 km + 19.08 km + 18.85 km= 68.31 km.
Answer: C. good reflector of heat
Explanation:
In space, sunlight transfers heat by radiation to objects and bodies and this includes satellites and astronauts. In addition, although the peak of the sun's emission is in the visible region of the electromagnetic spectrum, a part is also emitted in infrared (transferring thermal energy or heat) and ultraviolet (especially in the upper part of the Earth's atmosphere).
That is why in space missions, objects and many satellites are covered by thin layers or sheets that reflect this thermal energy and thus avoid damaging the equipment due to high temperatures.
In this sense, among the reflective materials used are aluminum, silver, copper and gold; the latter being the most used because it does not corrode or oxidize (unlike silver and copper) and is more malleable than aluminum.
On the other hand, <u>astronauts are also vulnerable to the effects of infrared radiation, especially their eyes</u>, since the human eye has no receptors in the infrared spectrum. <u>That is why the astronaut's helmet visor is covered with a thin layer of gold to avoid the dangerous effects of solar radiation.</u>
<span>The runner is moving by uniformly accelerated motion, starting from rest (so, his initial velocity is zero). The law of motion of the runner is
</span>

<span>
where x(t) is the distance covered after time t, and a is the acceleration of the runner. By re-arranging the formula, we get
</span>

<span>
We know the runner has covered a distance of S=12m in t=4.0 s, and if we plug these numbers into the equation, we find the acceleration of the runner:
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<span>
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