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!

Homework Help: Momentum Projectile problem

  1. Dec 22, 2008 #1
    1. The problem statement, all variables and given/known data
    A 9.3 kg firework is launched straight up and at its maximum height 45 m it explodes into three parts. Part A (0.5 kg) moves straight down and lands 0.29 seconds after the explosion. Part B (1 kg) moves horizontally to the right and lands 10 meters from Part A. Part C moves to the left at some angle. How far from Part A does Part C land (no direction needed)?

    2. Relevant equations

    3. The attempt at a solution
    can you check my work
    1. Momentum for part A:
    y = (Vo)t - (1/2)(9.8m/s^2)t^2
    Substitute the values for y and t which are given. Solve for Vo, the initial downward velocity. Multiply the value of Vo by 0.5 kg to get the initial momentum down of A.
    momentum A = 78.2967
    2. Momentum for part B:
    y = (1/2)gt^2 = 45m for its downward motion.
    substitute the value of g and solve for t.
    Vx = 10/t = 10/3.03 = 3.3m/s
    momentum B = (1kg) (Vx) = 3.3

    3. Resultant of the two momentums:
    Did a vector addition of the momentums of A and B. The resultant will be a vector downward to the right. Determine both, magnitude and direction.
    4. Momentum of part C:
    That is opposite (equilibrant) of of the vector sum of A and B.
    momentum C =(momA ^2 + momB ^2) ^0.5 = 78.3662
    Divide the momentum of C by its mass to get the initial velocity of C.
    Voc = 10.046m/s
    i am stuck at this point please help thanks
  2. jcsd
  3. Dec 22, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi myoplex11! :smile:

    Very good technique so far. :biggrin:

    Now the trick is to split C's velocity into horizontal and vertical components :wink:

    (so you find t from the vertical one, and use that to find the horizontal distance)
  4. Dec 22, 2008 #3
    But how can i split C's velocity i dont know the angle?
  5. Dec 22, 2008 #4


    User Avatar
    Science Advisor
    Homework Helper

    uhhh? … mCViC = -mAViA - mBViB. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook