OT: PHYSICS QUESTION please help sfsuphysics =)

moo0o

Premium Member
need help with a physics problem. actually i know the physics, or atleast i think i do.

anyway here it is

phhysiics.jpg


SO far ive found the two vectors which of course is the easy part.

for vector two, i cant seem to find the angle or x and y components. am i attempting this all wrong? first question, and the rest of the questions if you have time.
 

sfsuphysics

New member
Geeze you have the word physics in your name.... ;)

Interesting way they have you do it, looks like they're purposefully trying to make you do more work than you need to. But then again finding the average acceleration is a bit more work for circular motion than instantaneous acceleration :D

First set up your coordinate system, polar coordinates would be a breeze but I'm guessing this problem wants Cartesian, so draw a circle, a find a place for your origin i.e. (0,0), my suggestion, right through the center of the circle, this way you exploit the symmetry of the circle.

Finding the first vector really is arbitrary, its a uniform speed in a circle, so any point you choose as V1 is going to be fine, lets make it easy, choose one that's right along either the x or y axis.. that way it will only have velocity components in the y or x direction (respectively), and the magnitude will be the velocity value that's given 5.60 m/s

The second vector, V2, requires a bit of work, and it depends upon your delta-t. Figure out how far the dog will go in that delta-t (using the velocity given) and that will be how much of that circle the dog will have gone. v * delta t = distance. Then you can work backwards and find what angle that is given remembering (hopefully) that the arclength of a circle (i.e. the distance traveled by the dog) [ s = r * angle ], a little bit of manipulation can get you that angle, and from there some sines and cosines should hopefully yield your x & y components of V2 and from there it should be a snap.

Let me know if this didn't help
 
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Dyngoe

New member
BTW, this isn't physics, it's Calculus. You need some sort of energy in the equation to cross the Physics barrier. So, I have an addition to the equation:
The poodle weighs 10g. What is the potential energy of the poodle in motion at 4 seconds?
:D
 

Dyngoe

New member
Khannnnn!!!! I was going for a trick question there! That's why I threw in the time factor to mislead everyone. Thanks for ruining my fun Mike. :p
 

rhaey

New member
"So if I'm riding a train that travels the speed of light and I get in front of the train and threw a ball ahead of the train, is the ball traveling faster than the speed of light?"(Young Einstein (1988))
 

Dyngoe

New member
Oh, that get's into a whole world of time not being constant and the effect of time as you approach "c". Run away from discussions like this, it will make your brain hurt. I think I had PTSD for a month when it was first proven to me. :D

BTW, good quote!
 

moo0o

Premium Member
Dang all I needed was that arclength formula. Knew there was a way to find degrees. And yes I agree it isn't physics but ehh it was a little bit too late for me to accept it as anything else. :) thanks again everyone and especiallly mike! Would you like to be my physics go to guy for the next few quarters? :).
 

chris4869

New member
Amazing. You guys still remember those stuff from school (other than mooOo who sounds like he's still in school :D )! I can't even remember what I had for lunch yesterday. :lol:
 

rhaey

New member
Physics one of those phenomenon that I would really love to learn, but for some reason the hamster in my head totally disagree with me and stops spinning the wheel.
 

tuberider

Where's Lahey?
Premium Member
Slightly OT, but my Physics teacher in HS looked over at me during the beginning of classes my senior year and said "Jeremy, you have no idea what I'm talking about do you?", of course since I was called out I said "yes". That person was none other than Jill Biden, Joe's wife, who somehow limped me through Algebra II, she was a great teacher.
 
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