Results 1 to 5 of 5

Math Help - A ladder problem...

  1. #1
    Member
    Joined
    Oct 2009
    Posts
    92

    Question A ladder problem...

    A 26 foot ladder is placed againts a wall.If the top of the ladder is sliding down at a rate of 2 feet per second,then estimate the rate at which the bottom of the ladder is moving away from the wall when the bottom of the ladder is 10feet away from the wall.

    Let height and base be h and b respectively.All I could understand was that we have to find db/dt,we are given dh/dt ..can somebody help me with this question?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by mathcalculushelp View Post
    A 26 foot ladder is placed againts a wall.If the top of the ladder is sliding down at a rate of 2 feet per second,then estimate the rate at which the bottom of the ladder is moving away from the wall when the bottom of the ladder is 10feet away from the wall.

    Let height and base be h and b respectively.All I could understand was that we have to find db/dt,we are given dh/dt ..can somebody help me with this question?
    http://www.mathhelpforum.com/math-he...ted-rates.html
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Sep 2009
    Posts
    151
    Let h(t) be the height at time t, b(t) be length of the base of the ladder from the wall at time t.

    Now we have

    h(t)^2+b(t)^2=26^2

    2h(t)\frac{dh}{dt}+2b(t)\frac{db}{dt}=0

    Since you know that the base is 10 feet away, at time t0 so b(t0)=10. And the ladder is sliding down at -2 feet per second \frac{dh}{dt}=-2, at time t0.
    So what is \frac{db}{dt} at time t0 ?

    Can you finish this one now?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Oct 2009
    Posts
    92

    Question


    Ok so we plug in the values for dh/dt as -2 and find out db/dt?

    For eg :

    2h(0)(-2)+2b(0)db/dt=0
    2h(0)(-2)+2(10)db/dt=0
    0+20db/dt=0
    20 db/dt=0
    db/dt=0..??
    I know Iam doing this wrong...where am I going wrong?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by mathcalculushelp View Post

    Ok so we plug in the values for dh/dt as -2 and find out db/dt?

    For eg :

    2h(0)(-2)+2b(0)db/dt=0
    2h(0)(-2)+2(10)db/dt=0
    0+20db/dt=0
    20 db/dt=0
    db/dt=0..??
    I know Iam doing this wrong...where am I going wrong?
    h(t) and b(t) tell you that h and b are functions of time ... you do not plug in 0 for t.

    when b = 10, h = 24
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. The problem of the ladder!
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: May 3rd 2011, 06:51 PM
  2. Sliding ladder problem
    Posted in the Calculus Forum
    Replies: 2
    Last Post: July 31st 2010, 07:22 PM
  3. Help with ladder triangle problem
    Posted in the Geometry Forum
    Replies: 3
    Last Post: July 5th 2009, 10:13 PM
  4. Optimization The ladder problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 21st 2009, 08:45 AM
  5. Challenging Ladder Problem
    Posted in the Geometry Forum
    Replies: 1
    Last Post: February 17th 2008, 06:03 PM

Search Tags


/mathhelpforum @mathhelpforum