Answer: Calc III: Find Div(F) in Terms of r

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To find the divergence of the vector field F defined as F = r/R^p, where r = xi + yj + zk and R = |r|, it is essential to express F in terms of x, y, and z first. The divergence can be computed by taking the gradient of F and summing the components. After some manipulation, it becomes clear that substituting r simplifies the process significantly. The discussion highlights that the initial complexity can be resolved by recognizing the relationship between the variables. Ultimately, expressing F in terms of r leads to a straightforward calculation of div(F).
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Homework Statement



Let r = x i + y j + z k and R = |r|. Let F = r/R^p.

find div(F) in terms of r.. i can't figure out how to express it in therms of r

Homework Equations



div(F) = the gradient added together
 
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First: express F in terms of x,y,z
Second: Compute the divergence of F by hand
Third: try to identify r in div F
 
hahaha sweet.. i figured it out. I was thinkin it was just too complicated but when you replace all the stuff with r it works out nicely.

thanks!
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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