Results 1 to 2 of 2

Math Help - SUVAT Question

  1. #1
    Junior Member Mist's Avatar
    Joined
    Oct 2009
    From
    Yorkshire
    Posts
    26

    SUVAT Question

    A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

    Any help?

    I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by Mist View Post
    A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

    Any help?

    I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.
    s = 8 (because we've gone from 0 to 8 on the line)
    t = t
    u = 12
    a = -5 (the minus sign is important)
    <br />
s = ut+ \frac{1}{2}at^2

    8 = 12t - \frac{5}{2}t^2

    Multiply through by 2 to clear the fraction and rearrange into the form ax^2+bx+c=0

    5t^2-24t+16=0

    Solve using your favourite method, this one does factorise

    (5t-4)(t-4) = 0 \: \: \therefore \: t = \frac{4}{5} \: \text{ or } \: t = 4


    To find the value find v at the given time

    v_1 = u+at_1 =12 - 4 = 8

    v_2 = u+at_2 = 12-20 = -8<br />

    Since v_2 < 0 it implies that the particle is now moving in the negative direction, back towards the origin. Therefore it follows that t = 0.8 is correct.

    oops, just saw that the question asks for the values of t (implying more than one solution) so if you quote both you should be correct and can disregard the stuff about v
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Mechanics 1 - SUVAT question
    Posted in the Math Topics Forum
    Replies: 0
    Last Post: April 14th 2010, 08:57 AM
  2. Another SUVAT Question
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: February 4th 2010, 11:46 PM
  3. SUVAT help please (mechanics)
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: January 19th 2010, 01:46 PM
  4. suvat question help
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: October 11th 2009, 11:52 AM
  5. Replies: 4
    Last Post: December 13th 2006, 05:48 PM

Search Tags


/mathhelpforum @mathhelpforum