lecture 2/25/21

 

Your password (updated)

is your asu id. Not your posting id. Not your campus id.  Not your social security number. Not your asurite userid.  

If you go to myasu profile Account Details window, under "My IDs" it's the one that says "ASU ID".  

It's also the one that everyone keeps wanting to send me in an unencrypted email, but is supposed to be PRIVATE INFORMATION.  That's why it's a good password--the university knows it, and you know it but no one else is supposed to know it.

Arithmetic kills!

https://www.youtube.com/watch?v=lcYkOh4nweE

And oh yeah, too many people aren't checking their arithmetic. 

Lecture 2/18/20

 

Lecture 2/16/21

 

Lecture 2/9/21

 

10.9#4 (edited)

I do not understand what the problem wants. I already took the derivative of r(t) and proceeded to take the magnitude of r'(t)=v(t). Then I was given a function in which I solved for t and got 2/7, which is not accepting that answer

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Not to contradict you, but you actually do seem to have a good understanding about what the problem wants.  The reason it's not accepting the answer is because it's the wrong answer.  I can't tell you exactly why, because you didn't send me your calculation. It looks the same way that the right answer does though, so my experienced guess is that you're making a simple algebra or arithmetic mistake.  

By the way, here's a trick: instead of finding the minimum of the speed ||v(t)||, find the minimum of the speed squared ||v(t)||^2=v(t).v(t).  It will give you the same answer but you don't have to deal with the square root (and dealing with the square root is a unnecessary complication that can cause mistakes).

Oh, ok, here we go. You just added an extra ^2 where there was none:

never mind I found the problem. I added a t^(2) to the y component of r(t). Thank you anyway for making me realize that I had a computation error

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You're welcome.  Yes most of the time people make these minor mistakes, and because they're so little they're easy to overlook.

Lecture 2/4/21