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Momentum Question

  1. Nov 7, 2005 #1
    Hey Everyone!! I dont quite understand how to figure this out....Any help would be greatly appreciated!
    The bird perched on the swing has a mass of 52.0 g and the base of the swing has a mass of 153 g. The swing and the bird are originally at rest, and then the bird takes off horizontally at 2.00 m/s. How high does the base of the swing rise above the original level? Disregard friction.
    Thanks!! ~*~Jazzy~*~
  2. jcsd
  3. Nov 7, 2005 #2
    Well, momentum is conserved, so find the velocity the swing will move back with.

    That would be the tangential velocity of the swing's circular motion because it is attached to the string.

    Now, figure out how you can use that tangential velocity to find out how high the swing would go if you treat it like a pendulum.
  4. Nov 7, 2005 #3
    how exactly do I use the tangential velocity to find the height?? Sorry if I sound like I'm dumb or something, but I dont really get physics too well....
  5. Nov 7, 2005 #4
    I really don't remember, I expected you to look it up. :) Let's see . . .

    How about this. You know the kinetic energy. You know the mass. You know gravity. The potential energy at it's top hight will be mgh. Since there is no friction, all the kinetic energy will turn into potential energy. Set (1/2)mv^2 equal to mgh and solve for h.

    Now there's nothing really left for you to do. :( I'm sure your happy though. ;)
  6. Nov 7, 2005 #5
    thanks - i just dont understand physics - if i would have known that i was going to have problems, i never would have taken it - my main problem is that my teacher doesnt teach - he just kinda presents the material, and i dont get it, so i have to try to teach myself, which is really hard when you have no inkling of what to do.....but Thank you so much for helping direct me on the right path!!! You have no idea how much it means to me!!
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