Vector Scalar Product and KE questions

AI Thread Summary
The discussion focuses on understanding scalar multiplication of vectors and finding angles between them, particularly using the formula cos(theta) = (a * b)/(|a||b|) for the dot product. The user initially struggled with questions from a physics set after missing a class on these topics. They successfully solved the first question using the kinetic energy formula k = 0.5 * m * v^2 but were unclear about the second question. Ultimately, the user reported that they figured out all the problems with assistance from others. The exchange highlights the importance of peer support in grasping complex physics concepts.
Walczyk
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Just a few questions from this set I have to do, I missed the class on these topics so I'm just a little confused with these last few problems.

http://img161.imageshack.us/img161/2307/problem43eu.png

Concerning sets 38-39, and 40-41, I've grasped how to scalar multiply these vectors, but not how to find the angle it seems, wondering if anybody can check those out. as for the last set, i was able to find the first answer with k=.5*m*v^2, but I'm not sure what the second question is asking. I missed the class on these topics (accelerated physics in the summer, awfully bad to miss a class). thanks in advance!
 
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I believe the formula you need to use is something like:

cos(theta) = (a * b)/(|a||b|)

Where * is the dot product of a and b.
 
aye, i wroked those angles out, inverse cosine.
edit: I've figured out all the problems, thanks for the help everyone.
 
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