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Average Velocity of a particle moving in a circle over a given interval 
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#1
Feb1711, 01:32 PM

P: 29

1. The problem statement, all variables and given/known data
2. Relevant equations d = 2.5 c = pi*d = 7.854 velocity/s ?= c * 2 = 15.7079 3. The attempt at a solution Since PR is 1/4 of the circle and the particle moves around the circle 2 times per second, I thought the average velocity would be 1/8th of the velocity that it's traveling. I'm really confused on this one. EDIT: I only need to solve for (a), that's why I only have data pertaining to that. Not worried about B and C, but any intuition on those is welcome. 


#2
Feb1711, 01:40 PM

P: 1,261

What is the definition of average velocity?



#3
Feb1711, 01:44 PM

P: 29

dx/dt = 1.25/.125 = 10? I'm not following 


#4
Feb1711, 01:51 PM

Mentor
P: 11,625

Average Velocity of a particle moving in a circle over a given interval
If someone were to show you two snapshots, the first showing the particle at P at time zero, and the second at point R at a time 1/8 second later, and you had no idea about the circular course, or what path the particle took to get from P to R, how would you go about finding the average velocity?



#5
Feb1711, 01:52 PM

Mentor
P: 11,625




#6
Feb1711, 02:11 PM

P: 29

The change in x is 1.25 and the change in time is 0.125 seconds, right? 


#7
Feb1711, 02:13 PM

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P: 11,625




#8
Feb1711, 02:20 PM

P: 29

1.25^2 + 1.25^2 = C^2 1.5625 + 1.5625 = C^2 3.125 = C^2 C = 1.767767 So .... The vector is (1.767767, 135 degrees)? 


#9
Feb1711, 02:26 PM

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P: 11,625

Okay! So you've got a distance vector. That gives you the displacement (magnitude of the vector) and the direction. Apparently the displacement happened in 1/8 second. So what's the average velocity vector?



#10
Feb1711, 02:38 PM

P: 29

So 14.1421 m/s? 


#11
Feb1711, 02:43 PM

Mentor
P: 11,625

Yup!
Remember though, that velocity is a vector. So you want to retain the angle information in your answer. 


#12
Feb1711, 02:45 PM

P: 29




#13
Feb1711, 02:55 PM

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P: 11,625

Build a man a fire and he'll be warm for a day. Set a man on fire and he'll be warm for the rest of his life! 


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