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Physics

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Two brothers are jogging, Josh and Drake. Josh has 1/2 the KE of Drake. Also, he is twice the mass of Drake. Plus, Josh had to increase his speed by 1.35 meters/second to achieve the same kinetic energy of Drake. What is the initial velocity?

  • Physics -

    JoshKE=1/2DrakeKE
    1/2Mj vj^2=1/4 Md Vd^2
    1/2 2Md Vj^2=1/4 Md Vd^2

    Vj^2=1/4 Vd^2

    Vj= 1/2 Vd

    but Vj+1.35 yields..
    1/2 *2Md(Vj+1.35)^2=1/2 Md Vd^2
    2(Vj+1.35)^2=Vd^2
    finally

    2(Vj+1.35)^2=4Vj^2
    Vj+1.35=Vj sqrt2
    Vj=1.35/.414=
    check all that.

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