1. Not finding help here? Sign up for a free 30min 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!

Exploding Object

  1. Oct 25, 2004 #1
    Alrighty, here is a problem I am stuck on.

    ----A 21.0-kg body is moving in the direction of the positive x axis with a speed of 274 m/s when, owing to an internal explosion, it breaks into three pieces. One part, whose mass is 7.5 kg, moves away from the point of explosion with a speed of 428 m/s along the positive y axis. A second fragment, whose mass is 3.5 kg, moves away from the point of explosion with a speed of 483 m/s along the negative x axis. What is the speed of the third fragment? Ignore effects due to gravity.-----

    Ok...so the momentum in the postive x direction before the explosion was p=mv...or 21x274= 5754 kg*m/s....i think the y direction is irrelevant in the problem, since momentum in the x axis is conserved...so assuming that, i do the equation 3.5kg x (-483 m/s) + 10kg x V3 = 5754 kg*m/s....the 2nd fragment's velocity is negative because it goes along the negative x axis...and the third fragment's mass is 10kg because 21-7.5-3.5 = 10kg. Anyway, I solved for the third fragment's velocity (V3) and got an answer of 744.45 m/s....but the computer program says I'm wrong. Does anyone know what I'm doing incorrectly? And if so, how do I go about the problem the correct way? Thanks so much. :D
  2. jcsd
  3. Oct 25, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    The momentum in the y-direction is definitely relevant; it is to be zero before and after the explosion..
  4. Oct 25, 2004 #3
    hmm..I'm not sure how to incorporate that though. I can find the velocity of the 3rd fragment in the y direction....(7.5 x 428) + 10x = 0...and I get -321 m/s. So...if I have the speed in the x component (744.45m/s) and in the y component (-321m/s)...how I do I find the fragment's speed? I'm not sure what I should be doing with that... :/

    ohhh...duh. I'm so dumb today. I just figured it out...do it like a triangle....744.45^2 + (-)321^2 = V^2.....ha. Thanks a bunch!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Exploding Object
  1. Exploding Object (Replies: 4)

  2. Object at rest explodes! (Replies: 16)

  3. Exploding object (Replies: 2)