1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Conservation of Momentum (Ch 7-9, Q6)

  1. Oct 12, 2014 #1
    1. The problem statement, all variables and given/known data
    A stationary bomb explodes in space breaking into a number of small fragments. At the location of the explosion, the net force due to gravity is zero newtons. Which one of the following statements concerning this event is true?
    (a) Kinetic energy is conserved in this process.

    (b) The fragments must have equal kinetic energies.

    (c) The sum of the kinetic energies of the fragments must be zero.

    (d) The vector sum of the linear momenta of the fragments must be zero.

    (e) The velocity of any one fragment must be equal to the velocity of any other fragment.


    2. Relevant equations
    Conservation of Momentum
    (mv) before = mv (after)

    3. The attempt at a solution

    (a) Kinetic energy is conserved in this process.
    This is a NO, because Kinetic energy isn't conserved, the energy is lost
    (b)
    The fragments must have equal kinetic energies
    I assume the fragments do not longer have Kinetic energy but Potential energy so its a NO
    (c)
    The sum of the kinetic energies of the fragments must be zero.
    Fragments do not longer have Kinetic energy as they are stationary, they have potential energy (I have no clue if this reasoning is correct) so the answer is NO
    (d) The vector sum of the linear momenta of the fragments must be zero.
    mass and velocity = 0 so Yes
    (e) The velocity of any one fragment must be equal to the velocity of any other fragment.
    The velocity is ZERO so they all have the same velocity so the answer is YES to this too (Is this correct? like some fragments can be having a velocity of 0 and others can have some movement still)
     
  2. jcsd
  3. Oct 12, 2014 #2

    gneill

    User Avatar

    Staff: Mentor

    You need to rethink what is going on here. Before the bomb explodes it is sitting stationary, so no kinetic energy. After it explodes, whatever energy powers the bomb (chemical, atomic,...) is turned into heat and kinetic energy of the fragments. The fragments scatter in all directions. Because the explosion takes place in space far from any large gravitational forces and without any friction to slow anything down, the fragments will all continue to travel indefinitely along straight paths.
     
  4. Oct 12, 2014 #3
    I see, that is why they said 0 gravity........brb
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Conservation of Momentum (Ch 7-9, Q6)
  1. Momentum conservation (Replies: 3)

Loading...