Results 1 to 8 of 8

Math Help - Calc I: velocity problem

  1. #1
    151
    151 is offline
    Newbie
    Joined
    Jan 2009
    Posts
    5

    Calc I: velocity problem

    Suppose an arrow is shot upward on the moon with a velocity of 39 m/s, then its height in meters after t seconds is given by h(t)=39t-0.83t^2. Find the average velocity over the given time intervals.

    [8, 9]:
    [8, 8.5]:
    [8, 8.1]:
    [8, 8.01]:
    [8, 8.001]:

    I understand that you need to figure out slope and simplify but my answer never comes out correctly.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by 151 View Post
    Suppose an arrow is shot upward on the moon with a velocity of 39 m/s, then its height in meters after t seconds is given by h(t)=39t-0.83t^2. Find the average velocity over the given time intervals.

    [8, 9]:
    [8, 8.5]:
    [8, 8.1]:
    [8, 8.01]:
    [8, 8.001]:

    I understand that you need to figure out slope and simplify but my answer never comes out correctly.
    really? are you sure you are using the right equation?

    note, the average velocity over the time interval [a,b] is given by

    \text{Avg Vel. } = \frac {h(b) - h(a)}{b - a}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    151
    151 is offline
    Newbie
    Joined
    Jan 2009
    Posts
    5
    yeah I'm using that equation but I changed it to look like this:
    [y(8+h)-y(8)]/[(8+h)-8]
    Follow Math Help Forum on Facebook and Google+

  4. #4
    151
    151 is offline
    Newbie
    Joined
    Jan 2009
    Posts
    5
    maybe my algebra skills are just horrible but for the average velocity equation, I simplifiied it and got this:
    [-.83h^2+25.72h+273]/h

    Is that even close?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by 151 View Post
    yeah I'm using that equation but I changed it to look like this:
    [y(8+h)-y(8)]/[(8+h)-8]
    why go through all that trouble?

    Quote Originally Posted by 151 View Post
    maybe my algebra skills are just horrible but for the average velocity equation, I simplifiied it and got this:
    [-.83h^2+25.72h+273]/h

    Is that even close?
    and no, it is not correct, but it is close.

    ...are you sure there should be 273 there?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    151
    151 is offline
    Newbie
    Joined
    Jan 2009
    Posts
    5
    The reason I altered to velocity equation is because that's what the example problem in the book did. If you use the original equation, how do you plug in the intervals?

    For the first interval, would it look like this?
    (39-.83(9)^2)-(39-.83(8)^2)/(9-8)
    Follow Math Help Forum on Facebook and Google+

  7. #7
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by 151 View Post
    The reason I altered to velocity equation is because that's what the example problem in the book did. If you use the original equation, how do you plug in the intervals?

    For the first interval, would it look like this?
    (39-.83(9)^2)-(39-.83(8)^2)/(9-8)
    yes, but you can continue doing it the first way, since you already went through all the trouble

    you have: \frac {25.72h - 0.83h^2}h

    your h values are 1, 0.5, 0.1, 0.01, 0.001
    Follow Math Help Forum on Facebook and Google+

  8. #8
    151
    151 is offline
    Newbie
    Joined
    Jan 2009
    Posts
    5
    Okay, thanks I got it now.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: February 23rd 2011, 09:17 AM
  2. Replies: 2
    Last Post: September 21st 2009, 02:32 PM
  3. Velocity problem!
    Posted in the Calculus Forum
    Replies: 3
    Last Post: August 13th 2009, 11:13 PM
  4. Velocity problem in calc
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 4th 2009, 06:51 PM
  5. velocity problem
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: September 24th 2008, 12:51 AM

Search Tags


/mathhelpforum @mathhelpforum