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Homework Help: Unknown Speed

  1. Dec 14, 2006 #1
    Unknown Speed!!

    Hi all, I've got this problem in my physics class I can't figure it out. Iv'e changed the values because I only wan't to know How we can solve this..

    Here it goes:

    I have a 400 g (3,29 N) Meteor that crashed in the earth surface and reach a depth of 1.7 m . The scientist say that the ground had a resistance force of 1,0 x 10^6 N.

    (We ignore the air's friction.)

    What was the meteor's speed?

    It's all I've got.

    Iv'e done a graphic on paper whit vectors But I don't quite get the methos of doing it.

    Else.. I tried Caluculating the potiential energy (Ep = mgh) but I don't have the height.. Neither de speed for the Kinetic energy (Ek = 1/2 m v^2)

    Bah.. Help me out! :P:P
  2. jcsd
  3. Dec 14, 2006 #2


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    Do you understand the relationship between force, distance, and work?

    W = F*d

    - Warren
  4. Dec 14, 2006 #3
    OHHH !! nevermind.. I get it!I will start working on it.
  5. Dec 14, 2006 #4
    Here is what I have done:

    W= Fr * Delta Sr
    W= 1000000 N * 1,7 m
    W= 1700000 J

    Ek = 1/2 * m * v^2
    1700000 j = 0.5 * 3,29 N * v^2
    1033434,65 j = v^2
    1016,58 m/s = V

    Meteor's speed is 1016,58 m/s
  6. Dec 14, 2006 #5


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    Be careful with your units. Mass should be in kilograms, not in newtons. Otherwise, yes, you have the right idea.

    - Warren
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