Results 1 to 3 of 3

Math Help - A ball is thrown upwards

  1. #1
    Newbie
    Joined
    Nov 2008
    Posts
    10

    A ball is thrown upwards

    Hey I am doing some exam questions from a mechanics textbook and I am really confused I was just wondering if anyone could help me out The question is:

    A ball is thrown upwards at 7ms from a point A which is 8m vertically above horizontal ground. Given that the ball moves freely under gravity find:

    the greatest height above the ground attained by the ball

    the speed of the ball the instant it when it strikes the ground


    Thanks alot


    A ball is thrown vertically upwards and takes 3 seconds to reach its highest point. Find the times at which the ball is 39.2m above its point of projection.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    May 2008
    From
    Melbourne Australia
    Posts
    210
    Thanks
    24
    Define the origin to be at ground level and up to be the positive direction. Let the position be called s, velocity v and acceleration a.

    We have a = -9.81 m/s/s due to gravity.
    s_0=8, v_0=7
    equation 1. s=s_0+v_0t+0.5at^2
    equation 2. v=v_0+at

    Now when the ball is at its highest it is neither going up nor down, that is v=0. So set equation 2 equal to zero and solve it for t, the time at which the height is maximum. Substitute this value of t into equation 1 to find the maximum height.

    For the second part set equation 1 equal to zero and solve for t, the time at which the ball hits the ground. Substitute this into equation 2 to find the velocity when the ball hits the ground. Since we defined the positive direction to be up, the answer will be negative.



    For your second question s_0=0, v_0 is not known. Use equation 2 with t=3 to find v_0, then you can find the required answer using equation 1 by solving for the only unknown (t).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2008
    Posts
    10
    thanks alot
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Ball thrown upwards
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: September 20th 2010, 06:17 PM
  2. Replies: 1
    Last Post: March 5th 2010, 11:46 AM
  3. Ball thrown vertically upwards
    Posted in the Advanced Applied Math Forum
    Replies: 9
    Last Post: April 13th 2008, 09:23 AM
  4. Thrown Ball problem
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: October 31st 2007, 12:24 AM
  5. A ball is thrown
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 7th 2007, 01:11 PM

Search Tags


/mathhelpforum @mathhelpforum