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: Kinetic Energy

  1. Oct 16, 2008 #1
    1. The problem statement, all variables and given/known data
    Find the total kinetic energy in the system. a explosion fires two pieces both 7.3m high and 11.2m horizontally total kinetic energy done by the explosion the first piece is 15kg, the second 26kg?


    2. Relevant equations
    kinematics
    Ke=1/2(mv2)


    3. The attempt at a solution
    I found that Vi(y) = [tex]\sqrt{2(9.81)(-7.3)}[/tex] = 11.96 m/s do i just use this to find the total energy done? or do i need to consider the x-dir as well, If so how do i do that?
     
  2. jcsd
  3. Oct 16, 2008 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi Grogerian!

    The KE depends on the total speed, as you know, so Vy is obviously not enough unless Vx is zero.

    (but I can't help any furher, as I don't understand the question. :redface:)
     
  4. Oct 16, 2008 #3

    LowlyPion

    User Avatar
    Homework Helper

    Velocity is the sum of the components, so yes, you do need to determine the x component.

    Since you can figure the time to drop 7.3m from the peak and you know that will be half the time of its flight, and you know that is 7.3m = 1/2 g*t2. Now you can figure how fast it was to go 11.3m.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook