The two different isotopes have weights :
w1 = 78.918 amu
w2 = 80.916 amu
average weight w3 = 79.903 amu
The mixing of two components can be modeled as
let the fraction of w1 be 'x'
hence 
now this is a linear equation in 'x'. Substituting the values we get
x = 0.507
hence the percentage of Br79 = 50.7% and the percentage of BR81 = 49.3%
Answer:
Friction force always acts tangent to the surface at points of contact. Friction force acts opposite to the direction of motion. There are 2 types of friction: Static friction: If the two surfaces in contact do not move relative to each other, one has static friction.
<h2>Answer:</h2><h3>D. ability to react with oxygen</h3><h2>Explanation:</h2>
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Answer:
The definitive and unifying theme or idea of a story or article. It encompasses all the aspects necessary to create a coherent main idea. The central idea is typically expressed as a universal truth or theme that is built and supported by the setting and characters in a story.
Explanation:
This is the correct answer to your question.
Hope this helps!!!
Kyle.
