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Finding time in circular motion 
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#1
Nov108, 04:06 PM

P: 20

1. The problem statement, all variables and given/known data
The tips of the blades in a food blender are moving with a speed of 15 m/s in a circle that has a radius of 0.052m. How much time does it take for the blades to make on revolution? 2. Relevant equations T=(2XpiXr)/T T: period of time it takes to complete one cycle 3. The attempt at a solution I tried using the equation under "relevant equations" and got 0.02seconds as an answer. This is wrong but I don't know what other equation to use.. 


#3
Nov108, 04:19 PM

P: 20

oh whoops. but.. i tried that and it still didn't work..
is there another equation that i should use instead? i feel that my T represents time, but not the one i'm looking for 


#4
Nov108, 04:26 PM

PF Gold
P: 619

Finding time in circular motion
Lets break it down. r = 0.052 meters. The circumference is 2 pi 0.052 which is 0.104 pi meters. It rotates at velocity 15 meters every second. So this means that it does 15/0.104 pi revolutions every second. Then just inverse that quantity to find how many seconds is one revolution



#5
Nov108, 04:40 PM

P: 20

i keep getting 0.02 seconds, but this isn't the right answer.
is this what you got, too? 


#6
Nov108, 05:02 PM

P: 70

V^2/r= 4 pi^2 r/T^2
solve for T EDIT: Forgot square T 


#7
Nov108, 05:18 PM

PF Gold
P: 619




#8
Nov108, 05:22 PM

PF Gold
P: 619




#9
Nov108, 06:03 PM

P: 70

Oh sorry I forgot to square the T (silly mistake)
its 4pi^2r/T^2 


#10
Nov108, 06:06 PM

PF Gold
P: 619




#11
Nov208, 02:42 PM

P: 20

haha, thanks anyways you guys.
you know, i think you guys are right. i'll talk to my teacher about changing the answer :) 


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