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Homework Help: Induced emf

  1. Mar 30, 2004 #1
    A 5.56m long steel beam is accidentally dropped by a construction crane from a height of 3.97m. The horizontal component of the Earth's magnetic field over the region is 28.4e-6T. Acceleration of gravity is 9.8 m/s^2.
    What is the induced emf in the beam just before impact with the Earth, assuming its long dimension remains in a horizontal plane, oriented perpendicularly to the horizontal component of the Earth's magnetic field?

    I sort of have an idea how to begin but the whole gravity thing is confusing me. Any help?
  2. jcsd
  3. Mar 30, 2004 #2
    I think that gravity only plays a role since you will want to know how fast the beam is traveling through the magnetic field just before it hits the ground.
  4. Mar 31, 2004 #3
    YUP! That's what I was thinking too. One of the equations for induced emf is E=Blv but how do I get the velocity from the gravity because i am not given a time period. It's probably something just basic...but I can't seem to grasp on it at this moment.
  5. Mar 31, 2004 #4
    Just use the kinematic equations. You are given the height it is falling from, and you know how fast it accelerates due to gravity.
    Without time, use [tex]v_{f}^2=v_{i}^2+2a(y_{f}-y_{i})[/tex]
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