Results 1 to 12 of 12

Math Help - Intergration and Vertical Motion

  1. #1
    Junior Member
    Joined
    Jun 2007
    Posts
    26

    Intergration and Vertical Motion

    Hi, I'd appreciate any help on this!

    1. With that velocity must an object be thrown upward from ground level to reach a max. height of 200 m?

    2. The acceleration due to gravity is -1.6 m/s on the moon. If a stone is dropped from a cliff and hits the surface 20 seconds later, what was its velocity at impact?

    Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member SengNee's Avatar
    Joined
    Jan 2008
    From
    Pangkor Island, Perak, Malaysia.
    Posts
    155
    Quote Originally Posted by alreadyinuse View Post
    Hi, I'd appreciate any help on this!

    1. With that velocity must an object be thrown upward from ground level to reach a max. height of 200 m?

    2. The acceleration due to gravity is -1.6 m/s on the moon. If a stone is dropped from a cliff and hits the surface 20 seconds later, what was its velocity at impact?

    Thanks!
    1)

    max height =s=200
    a=g=-10
    v=0
    u=?

    v^2=u^2+2as
    0=u^2+2(-10)(200)
    u=20(10)^{\frac {1}{2}}



    2)

    a=g=+1.6(drop, therefore positive)
    t=20
    u=0
    v=?

    v=u+at
    v=(0)+(+1.6)(20)
    v=32 (positive just the direction)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,212
    Thanks
    419
    Awards
    1
    I just want to mention here that g = 9.8~m/s^2, not 10.

    -Dan
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member SengNee's Avatar
    Joined
    Jan 2008
    From
    Pangkor Island, Perak, Malaysia.
    Posts
    155
    Quote Originally Posted by topsquark View Post
    I just want to mention here that g = 9.8~m/s^2, not 10.

    -Dan

    I know that, but I only a Form 5 student just after SPM(same standard as "O" level). In SPM, g=10m/s^2 when doing calculation.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Aug 2007
    From
    USA
    Posts
    3,111
    Thanks
    2
    Quote Originally Posted by SengNee View Post
    I know that, but I only a Form 5 student just after SPM(same standard as "O" level). In SPM, g=10m/s^2 when doing calculation.
    What? Gravity changes depending on what level class you are in!?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member SengNee's Avatar
    Joined
    Jan 2008
    From
    Pangkor Island, Perak, Malaysia.
    Posts
    155
    Quote Originally Posted by TKHunny View Post
    What? Gravity changes depending on what level class you are in!?
    I not mean that.
    Front pages of SPM Physics Paper list formula and constant for us.
    g=9.8≈10
    In the Physics Paper, the constant g listed as g=10 and our calculation also use g=10 to make our calculation easier.

    I'm sorry about that, I will use g=9.8 next times.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Senior Member
    Joined
    Dec 2007
    From
    Melbourne
    Posts
    428
    Maylasia is not alone in using this bewildering approximation: In Australia (or Victoria at least), acceleration due to gravity is 10m/s^2 until you reach university level.
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,212
    Thanks
    419
    Awards
    1
    Quote Originally Posted by badgerigar View Post
    Maylasia is not alone in using this bewildering approximation: In Australia (or Victoria at least), acceleration due to gravity is 10m/s^2 until you reach university level.
    I've heard of a couple of US High Schools that do this too. Apparently it is an effort to make the numbers "easier" for the students.

    -Dan
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Member SengNee's Avatar
    Joined
    Jan 2008
    From
    Pangkor Island, Perak, Malaysia.
    Posts
    155
    Quote Originally Posted by badgerigar View Post
    Maylasia is not alone in using this bewildering approximation: In Australia (or Victoria at least), acceleration due to gravity is 10m/s^2 until you reach university level.
    So, why they keep on said that g must equal to 9.8.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,212
    Thanks
    419
    Awards
    1
    Quote Originally Posted by SengNee View Post
    So, why they keep on said that g must equal to 9.8.
    Because that is a lot closer to the measured value? I'm not sure what you mean?

    For the record I am against making the numbers easier on the students. There was a survey done (sometime in the mid 80s?) where students who had done all their schoolwork in problems where the numbers always canceled out nicely etc, etc. This was fine until they got to the real world and the numbers got ugly. The problem was that they had no confidence in their answers if it didn't come out to be a nice integer.

    For the Applied Sciences anyway, I say that decimal numbers rule!

    -Dan
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by topsquark View Post
    I've heard of a couple of US High Schools that do this too. Apparently it is an effort to make the numbers "easier" for the students.

    -Dan
    It's very very ridiculous.

    In this day and age of ubiquitous technology, that you would prescribe g = 10 rather than 9.8 in "an effort to make the numbers "easier" for the students" is diabolical.

    Some of the folk sitting on these curriculum panels need to have a good hard look at themselves ....
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by topsquark View Post
    Because that is a lot closer to the measured value? I'm not sure what you mean?

    For the record I am against making the numbers easier on the students. There was a survey done (sometime in the mid 80s?) where students who had done all their schoolwork in problems where the numbers always canceled out nicely etc, etc. This was fine until they got to the real world and the numbers got ugly. The problem was that they had no confidence in their answers if it didn't come out to be a nice integer.

    For the Applied Sciences anyway, I say that decimal numbers rule!

    -Dan
    Hear hear.

    I am in complete agreement with you.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. vertical motion mechanics problem
    Posted in the Math Topics Forum
    Replies: 5
    Last Post: March 25th 2010, 01:15 PM
  2. [SOLVED] vertical motion
    Posted in the Calculus Forum
    Replies: 6
    Last Post: January 1st 2010, 07:07 PM
  3. Motion in a vertical circle
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: December 19th 2009, 07:34 AM
  4. Vertical motion problem?
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: March 25th 2008, 08:14 PM
  5. vertical motion
    Posted in the Algebra Forum
    Replies: 1
    Last Post: June 7th 2007, 03:26 PM

Search Tags


/mathhelpforum @mathhelpforum