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March 28, 2017

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Starting from rest, a skier slides 100 m down a 28 degree slope.How much longer does the run take if the coefficient of kinetic friction is 0.17 instead of 0?

  • Physics - ,

    Case 1: zero friction
    F=mg sin(28)
    a=F/m=g sin(28)
    S=ut+(1/2)at²
    100=0+g sin(28)t²/2
    t=sqrt(2*100/(g sin(28))
    =6.59 s.

    Case 2: μk=0.17
    Frictional force
    =μmg cos(28)
    Net force (assuming μcos<sin)
    =mg(sin(28)-μcos(28)
    t=sqrt(2*100/(g (sin(28)-μcos(28))
    =7.99 s

    Take the difference.

  • Physics - ,

    shouldn't case 1 be cos(28) lol

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