Child on a Merry-Go-Around

  • Thread starter bewger
  • Start date
  • #1
6
0

Homework Statement


In the figure below, a 30 kg child stands on the edge of a stationary merry-go-round of mass 100 kg and radius 2.0 m. The rotational inertia of the merry-go-round about its rotation axis is 150 kg·m2. The child catches a ball of mass 1.1 kg thrown by a friend. Just before the ball is caught, it has a horizontal velocity v of magnitude 11 m/s, at angle ϕ = 37° with a line tangent to the outer edge of the merry-go-round, as shown. What is the angular speed of the merry-go-round just after the ball is caught?


11-54.gif

Homework Equations


p = mv
L = Iw


The Attempt at a Solution



So I'm assuming that angular momentum is conserved. Thus,

mv = Iw
I found the total I.
I_merrygoaround = 150
I_child = MR^2 = 120
I_ball = MR^2 = 1.1(rsin(phi))^2 = 1.44
I_total = 271.44

[tex]\omega[/tex] = (mv) / (I_total) = 12.1/271.44 = 0.0445 rad/s

But this is incorrect.
What did I do wrong?

Homework Statement





Homework Equations





The Attempt at a Solution

 

Attachments

  • 11-54.gif
    11-54.gif
    7.8 KB · Views: 419

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
251
hi bewger! :smile:

you seem to be mixing up the angular momentum of the ball before with the angular momentum of the ball after :wink:
 
  • #3
6
0
Hi tiny-tim

I'm trying to figure out my mistake with your advice, but I'm a little stumped by what you mean by that.

Can you elaborate on that?
 
  • #4
tiny-tim
Science Advisor
Homework Helper
25,832
251
hi bewger! :smile:

I'm finding it a little difficult to read what you posted (try using the X2 tag just above the Reply box :wink:), but I don't think you've included both the angular momentum of the ball before and the different angular momentum of the ball after :smile:
 

Related Threads on Child on a Merry-Go-Around

  • Last Post
Replies
4
Views
2K
Replies
6
Views
4K
  • Last Post
Replies
6
Views
7K
Replies
3
Views
773
Replies
8
Views
5K
  • Last Post
Replies
9
Views
3K
Replies
1
Views
4K
Top