SUPER CONFUSING linear algebra question

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The discussion revolves around a confusing linear algebra question involving angular velocity and vector operations. The term "omega" refers to angular velocity, measured in radians per unit time, and is represented as a vector multiplied by the unit vector of the rotation axis. Participants express confusion over the steps in the solution, particularly regarding the multiplication by (1,1,1) and the cross product with the direction of the rod. A general relation is highlighted where the rotation axis crossed with the position vector equals velocity. The conversation emphasizes the need for clarity in understanding these concepts to solve the problem effectively.
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SUPER CONFUSING linear algebra question :)

Homework Statement


I have attached a picture of the question with a solution.

The Attempt at a Solution


Well... First i found the parametric equation of the vector L... Yeah...

So even looking at the solution I am confused. I get the conversion that they made to rad/s but the steps after that blow my mind :|. What does omega mean and also why did they multiply by (1,1,1) and then took the cross product of this point and the direction of the rod?

I want to get through this step by step.

Thank you!
 

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where's the pic ;)
 


susskind_leon said:
where's the pic ;)

Wow I was so excited I forgot about the picture LOOL
 


Lol
So, Omega means angular velocity (how many rads per unit time, in this case, minute). You should look it up on wikipedia, it reveals useful information for you.
Omega vector is the angular velocity times the unit vector of the rotation axis, which is (1,1,1)/sqrt(3)
Now, rotation axis cross position vector equals velocity is a general relation.
(If you don't believe me, look at a circularly rotating particle in the xy-plane, for example. Compute the velocity by taking d/dt r(vec). You will see, it holds. Now do the same in the xz- and yz-plane and argue that you can choose any plane.)
Now you only need to take the length of v and you're done.
 
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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