Results 1 to 6 of 6

Math Help - Finding Formula for Velocity

  1. #1
    Member
    Joined
    Nov 2008
    Posts
    90

    Finding Formula for Velocity

    I have a word problem stating a jet needs a speed of 200 mph to take off
    if it can accerlate from 0 to 200 mph in 30 seconds

    how long must the runway be (assume assume constant acceleration)

    How would I find a proper formula for velocity
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Calculus26's Avatar
    Joined
    Mar 2009
    From
    Florida
    Posts
    1,271
    Assuming Constant acceleration a(t) = 20/3

    Integrate to find velocity

    then v(t) = 20/3 t since the initial velocity is 0 this is the velocity.

    Integrate to find position (in this case same as distance)


    d(t) = 10/3 t^2

    d(30) = 3000
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Nov 2008
    Posts
    90
    how did you get 20/3
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member Pinkk's Avatar
    Joined
    Mar 2009
    From
    Uptown Manhattan, NY, USA
    Posts
    419
    20/3 won't really work because the time units are different; a(t)=\frac{20}{3}\frac{mi}{hr\cdot s}. You'll have to convert it to \frac{mi}{s^{2}}, \frac{mi}{hr^{2}} or some other units that you'll feel most comfortable with.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Senior Member Pinkk's Avatar
    Joined
    Mar 2009
    From
    Uptown Manhattan, NY, USA
    Posts
    419
    Quote Originally Posted by sk8erboyla2004 View Post
    how did you get 20/3
    Well, think of acceleration as the slope of the velocity graph, or in other words, the change in velocity over the change in time. He did: \frac{200 mph - 0 mph}{30 s - 0 s}=\frac{20 mph}{3 s}=\frac{20}{3}\frac{mi}{hr\cdot s}
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor Calculus26's Avatar
    Joined
    Mar 2009
    From
    Florida
    Posts
    1,271
    argh !!! mixed units was thinking 200/30

    200mph = 293.3ft/sec

    it shoud be 293.3/30 = 9.78

    v(t) = .978 t

    then d(t) = .489*t^2

    d(30) = 440 ft
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Formula for Velocity/Angle compare?
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: May 24th 2010, 06:44 AM
  2. Finding the initial velocity
    Posted in the Advanced Math Topics Forum
    Replies: 3
    Last Post: May 6th 2010, 11:13 PM
  3. Replies: 1
    Last Post: April 26th 2010, 07:16 PM
  4. Velocity formula from a position formula
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 5th 2009, 02:50 PM
  5. Finding distance, given velocity with cos.
    Posted in the Calculus Forum
    Replies: 7
    Last Post: September 7th 2008, 11:17 AM

Search Tags


/mathhelpforum @mathhelpforum