Results 1 to 3 of 3

Math Help - Physics - Dynamics

  1. #1
    Senior Member sakonpure6's Avatar
    Joined
    Sep 2012
    From
    Canada
    Posts
    384
    Thanks
    28

    Physics - Dynamics

    Hi I am having trouble with the following question. Any help would be highly appreciated!
    A box accidentally falls from the back of a truck and hits the ground with a speed of 15.0m/s. It slides along the ground for a distance of 45m before coming to rest.
    a) find the length of time the box slides before stopping
    My attempt was using the equation d=v1*t + 0.5*a*t^2 where a = 9.8m/s^2 because the box fell out of the car. So i had to solve a quadratic and I got t about 111s. Is that right?

    Thank you for your time!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jun 2009
    Posts
    660
    Thanks
    133

    Re: Physics - Dynamics

    You need to find the (assumed) constant acceleration (retardation) of the box as it slides along the ground, and there is no reason to assume that this is -9.8m/s.
    Start by using the formula
    v^{2}=u^{2}+2as to find a, and then v=u+at to find t.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member
    Joined
    Oct 2012
    From
    Ireland
    Posts
    586
    Thanks
    155

    Re: Physics - Dynamics

    It is friction not gravity which is decelerating the box. In (quite accurate) theory the friction will decelerate it at a constant rate.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Dynamics 4
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: September 2nd 2009, 04:28 AM
  2. Dynamics 3
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: September 2nd 2009, 04:27 AM
  3. Dynamics
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: June 28th 2009, 01:14 AM
  4. how do solve quantum physics or physics equations
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: March 26th 2008, 04:33 AM
  5. 12U Physics - Motion and Dynamics! Please Help!
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: March 24th 2008, 08:22 PM

Search Tags


/mathhelpforum @mathhelpforum