Results 1 to 2 of 2

Math Help - Kinematics question

  1. #1
    Newbie
    Joined
    Oct 2008
    Posts
    7

    Kinematics question

    1. Two railway stations are 2km apart. A train starts from station with an acceleration of x m/s^2 for a certain time and then retards at 2x m/s^2 until it reaches the next station. It travels for a total time of 2 minutes. Find the value of x and the greatest speed attained.

    2. A train passes a station A at 30 km/h, maintains this speed for 7km and is then uniformly retarded to stop at B, 8km from A. A second train starts from A at the instant the first train passes it. It is uniformly accelerated for part of the way and uniformly retarded at the same rate for the rest of the way to stop at B at the same time that the first train stops. Find the greatest speed of the second train.

    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    16,427
    Thanks
    1857
    Quote Originally Posted by TrueTears View Post
    1. Two railway stations are 2km apart. A train starts from station with an acceleration of x m/s^2 for a certain time and then retards at 2x m/s^2 until it reaches the next station. It travels for a total time of 2 minutes. Find the value of x and the greatest speed attained.
    What is the difficulty? You know, I presume, that starting with intial speed [tex]v_0[/itex] and acceleration a, you move a distance \frac{1}{2}at^2+ v_0t in time t. Let t_1 be the time used to accelerate and t_2 be the time used to decelerate. You know that t_1+ t_2= 2 minutes. The train travels distance \frac{1}{2}at_1^2 and reaches speed xt_1. It then decelerates at -2x for time t_2 and so travels a distance -xt_2^2+ (xt_1)t_1= x(t_1^2- t_2^2)= 2km

    [/quote]2. A train passes a station A at 30 km/h, maintains this speed for 7km and is then uniformly retarded to stop at B, 8km from A. A second train starts from A at the instant the first train passes it. It is uniformly accelerated for part of the way and uniformly retarded at the same rate for the rest of the way to stop at B at the same time that the first train stops. Find the greatest speed of the second train.

    Thanks.
    [/QUOTE]
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Kinematics question.
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 6th 2011, 03:58 PM
  2. Need help with a kinematics question
    Posted in the Calculus Forum
    Replies: 5
    Last Post: March 17th 2011, 01:15 AM
  3. Kinematics Question
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: April 18th 2010, 09:25 AM
  4. Kinematics question
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: October 8th 2009, 05:34 PM
  5. Kinematics question
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: July 13th 2009, 12:09 AM

Search Tags


/mathhelpforum @mathhelpforum