Results 1 to 2 of 2

Thread: Mechanics 1 - Pulley Question, Why does the rope become slack when particle moving?

  1. #1
    Newbie
    Joined
    Mar 2017
    From
    UK
    Posts
    1

    Thumbs down Mechanics 1 - Pulley Question, Why does the rope become slack when particle moving?

    i've managed to do parts a,b,c,d ,e but not f.

    Figure 4 shows two particles P and Q, of mass 3 kg and 2 kg respectively, connected by a light inextensible string. Initially P is held at rest on a fixed smooth plane inclined at 30 to the horizontal. The string passes over a small smooth light pulley A fixed at the top of the plane. The part of the string from P to A is parallel to a line of greatest slope of the plane. The particle Q hangs freely below A. The system is released from rest with the string taut.
    Acceleration = 0.98 ms-2
    T= 18N


    On release, Q is at a height of 0.8 m above the ground. When Q reaches the ground, it isbrought to rest immediately by the impact with the ground and does not rebound. Theinitial distance of P from A is such that in the subsequent motion P does not reach A.
    Find(e) the speed of Q as it reaches the ground,(2)
    v= 1.25ms-1

    (f) the time between the instant when Q reaches the ground and the instant when thestring becomes taut again.

    I get how you tackle part f but i dont get why the tension would be lost in P? could someone please explain...
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    15,878
    Thanks
    3525

    Re: Mechanics 1 - Pulley Question, Why does the rope become slack when particle movi

    P is moving up the incline when Q hits the ground and has sufficient momentum to continue moving up the incline causing slack in the string.

    Q hits the ground at v = 1.25 m/s $\implies$ P's velocity is also v = 1.25 m/s up the incline at Q's impact time ... P will move an additional $t = \dfrac{v}{g\sin(30)} \, sec$ up the incline ... it will take the same amount of time for P to return to its position when Q hit the ground.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. mechanics pulley problem
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: Jan 8th 2013, 07:07 PM
  2. Mechanics String and PUlley problems
    Posted in the Math Topics Forum
    Replies: 8
    Last Post: Oct 15th 2012, 01:12 PM
  3. Mechanics 1 - pulley question.
    Posted in the Advanced Applied Math Forum
    Replies: 3
    Last Post: May 21st 2009, 05:39 PM
  4. Replies: 1
    Last Post: May 21st 2009, 12:27 PM
  5. Mechanics Of A Pulley
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: Dec 11th 2007, 06:37 AM

Search tags for this page

Click on a term to search for related topics.

/mathhelpforum @mathhelpforum