1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnetic sphere moving through iron dust; find velocity & other things

  1. Oct 1, 2013 #1
    1. The problem statement, all variables and given/known data
    A small magnetic sphere of initial mass Mo and initial radius Ro is moving through a space filled with iron dust. During its motion, 5% of displaced dust is deposited uniformly onto the surface of sphere. Given the density of dust to be ρ, find:
    1. relation rate of increase in radius and velocity
    2. if the magnet is moving under a force F=k(R^3), along the direction of motion, obtain a differential equation for radius at time t, when mass at time t, is much greater than it's initial mass and radius much greater that it's initial value
    3. assuming a particular solution of differential equation to be R=b(t^2), find the value of acceleration of magnet ball at time t.

    (b,k are constants)


    2. Relevant equations
    F(external)=0 => ΔP=0
    dm = 4∏ρ(R^2)dR



    3. The attempt at a solution
    couldn;t get any further that writing the above 2 equations
     
    Last edited: Oct 1, 2013
  2. jcsd
  3. Oct 1, 2013 #2

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    your second equation doesn't make sense dimensionally. The LHS is M/T while the right is just M.
    Suppose the ball is moving at speed v = v(t). How much dust is displaced in time dt? So how much is deposited, and how much does the radius increase by?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Magnetic sphere moving through iron dust; find velocity & other things
Loading...