physics kinetic energy

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a) if a particle's speed decreases by a factor of four, by what factor does its kinetic energy change?
b) particle A has three times the mass and twice the kinetic energy of particle B. What is the speed ratio VA / VB?

  • physics kinetic energy -

    a) KE = (1/2) M V^2

    What happens to KE when you replace V with a number 4 times larger?

    If you can't do that "in your head", try calculating the raio of kinetic energies
    KE2/KE1 = (4V)^2/V^2 = ?

    b) KEb = KEa/2
    KEb/KEa = (Mb/Ma)*(Vb/Va)^2 = 1/2
    = (1/3)*(Vb/Va)^2

    Solve for Va/Vb

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