Two types of chemical bonds common in compounds are covalent bonds and ionic bonds. The elements in any compound are always present in fixed ratios. Example 1: Pure water is a compound made from two elements - hydrogen<span> and </span>oxygen<span>.</span>
The answer is d. particles move from an area of high concentration to low concentration.
Answer:

Explanation:
<h3><u>Given data:</u></h3>
Acceleration = a = 0.4 m/s²
Initial Speed =
= 20 m/s
Final Speed =
= 40 m/s
<h3><u>Required:</u></h3>
Time = t = ?
<h3><u>Formula:</u></h3>

<h3><u>Solution:</u></h3>
Rearranging formula for t
![\displaystyle t =\frac{V_f-V_i}{a} \\\\t = \frac{40-20}{0.4} \\\\t = \frac{20}{0.4} \\\\\boxed{t = 50 \ seconds}\\\\\rule[225]{225}{2}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20t%20%3D%5Cfrac%7BV_f-V_i%7D%7Ba%7D%20%5C%5C%5C%5Ct%20%3D%20%5Cfrac%7B40-20%7D%7B0.4%7D%20%5C%5C%5C%5Ct%20%3D%20%5Cfrac%7B20%7D%7B0.4%7D%20%5C%5C%5C%5C%5Cboxed%7Bt%20%3D%2050%20%5C%20seconds%7D%5C%5C%5C%5C%5Crule%5B225%5D%7B225%7D%7B2%7D)
Question:
How could you use a model to show the cause-and-effect relationship between Earth's rotation and the apparent motion of the stars across the night sky?
Answer:
Gravity? or density because of the pull from the sun.