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Angular speed of yo-yo

  • Thread starter cecico
  • Start date
  • #1
15
0
Hi~
This is the question i got
A yo-yo has radius 8.00cm and mass 0.180kg with small hoop.
The yo-yo is released at rest and after yo-yo
descended 75.0cm calculater the angular speed of the rotating yo-yo
and the speed of its center.
I tried to use K=1/2Mv^2+1/2IW^2 but i got weird number....
I have the answer but I need t know how to solve it...
Just in case the answer for angular speed is 33.9rad/s and
the speed of its center is 2.71m/s.
I'm seriously fall into the deep~~~~ocean.
 

Answers and Replies

  • #2
hage567
Homework Helper
1,509
2
Don't forget about gravitational potential energy...
 
  • #3
Dick
Science Advisor
Homework Helper
26,258
618
The given answer is right. What did you do wrong? You aren't giving us near enough information to tell. What did you use for I?
 
  • #4
15
0
I use MR^2 for I.........
 
  • #5
13
0
Wouldn't I be

[tex]
I = \frac{m r^2}{2}
[/tex]

which is the one for a solid disk? Or are we considering the fact that the yo-yo is made up of two disks?
 
  • #6
Dick
Science Advisor
Homework Helper
26,258
618
Wouldn't I be

[tex]
I = \frac{m r^2}{2}
[/tex]

which is the one for a solid disk? Or are we considering the fact that the yo-yo is made up of two disks?
The clue refers to a hoop, so I think the do want you to use mr^2. You get the correct answer that way. But we still don't know enough to tell where cecico went wrong.
 

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