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March 28, 2017

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Part A:
A cardinal (Richmondena cardinalis) of mass 4.50×10^−2 kg and a baseball of mass 0.142 kg have the same kinetic energy. What is the ratio of the cardinal's magnitude p(c) of momentum to the magnitude p(b) of the baseball's momentum?

Part B:
A man weighing 650 N and a woman weighing 460 N have the same momentum. What is the ratio of the man's kinetic energy K(m) to that of the woman K(w)?

  • PHYSICS - PLEASE HELP - ,

    A. 0.5Mc*Vc^2 = 0.5Mb*Vb^2.
    0.5*0.045*Vc^2 = 0.5*0.142*Vb^2
    0.0225(Vc)^2 = 0.071(Vb)^2
    Vc^2 = 3.156Vb^2.
    Vc = 1.77Vb

    Mc*Vc/Mb*Vb
    Replace Vc with 1.77Vb:
    Mc*1.77Vb/Mb*Vb
    0.045*1.77Vb/(0.142*Vb
    0.07965Vb/0.142Vb = 0.561 = Momentum of
    Cardinal/Momentum of baseball.

    B. m1*g = 650 N.
    m1=650/g=650/9.8 = 66.3 kg.=Mass of man

    m2*g = 460 N.
    m2=460/9.8 = 46.94 kg. = Mass of woman.

    m1*V1 = m2*V2.
    66.3V1 = 46.9V2
    V2 = 1.414V1.

    K1/K2 = 0.5m1*V1^2/0.5m2*V2^2
    K1/K2 = 0.5*66.3*V1^2/0.5*46.9*V2^2
    K1/K2 = 33.15V1^2/23.45V2^2
    Replace V2 with 1.414V1:
    K1/K2 = 33.15V1^2/23.45*(1.414V1)^2
    K1/K2 = 33.15V1^2/46.9V1^2 = 0.707.

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