6道微积分数学题 国外大学的

1个回答

  • dv/dt=a=F/m=-g

    v=v0-gt

    s=int v dt=v0t-.5gt^2

    Assume the height of the cliff is h

    then

    (1) -h=v01t-.5gt^2

    (2) -h=v02(t-1)-.5g(t-1)^2

    (1)-(2) 0=48t-24(t-1)-16[t^2-(t-1)^2]

    0=24t+24-16(2t-1)

    8t=40

    t=5

    From(1)

    h=16t^2-v01t=16*5^2-48*5=400-240=160 ft

    -----------------------------------------------------------

    dv/dt=16

    v(end)=0

    v=v0-16t

    t=v0/16

    v0=16t

    S=int vdt=v0t-8t^2=200

    8t^2=200

    t=5

    v0=16*5=80ft/s

    -------------------------------------------------------------

    The increase of the population from time t=0 to t=16

    The population at t=16

    -------------------------------------------------------------

    Since slope=derivative,so the integral means the increase of the height form x=3 to x=5

    --------------------------------------------------------------

    f'(x)=df/dx=pounds/feet

    int f(x)dx=pounds*feet

    --------------------------------------------------------------

    The points are

    pi/n,2pi/n,...,npi/n

    The interval is (0,pi)

    so h=(pi-0)/n=pi/n

    The sum can be rewritten as

    int sin(x)dx

    =-cosx|

    =2