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!

Dymanics motion/energy/power, any help would be great

  1. Aug 13, 2008 #1
    I state my problen in my solution
    A big gun had a range of 120 km, a 37.5 m barrel, a muzzle velocity of 1550 m/s and fired a 120 kg shell.
    a) If you assume the shell’s acceleration to be constant, what maximum power was transferred to the shell as it travelled along the barrel? [5 Marks]
    b) What average power was transferred to the shell? [3 Marks

    MY solution

    okay so i went about it finding acceleration


    so now i have a=32033.33m/s^2

    then using Newtons law




    this is my first question is it fair to say d=37.5m or is it 120km??
    well thats what i have done


    second question how do i find time?

    third question is the above finds the total power yes? how do i find max power, does it mean its the power at a point? and is average pwoer just total power/distance? to find part b
  2. jcsd
  3. Aug 13, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    For part a you would use the length of the barrel. The other info given is that the shell undergoes constant acceleration in the barrel and has a final speed of 1550m/s at the end of the barrel. One can work out the time from that. Maximum power I think will be instantaneous power, which is the force multiplied by the velocity. Average power is what you've been calculating.
  4. Aug 14, 2008 #3
    ahh so you mean the v=u+at and solve for t

    and that makes sense about the max power thanks
  5. Aug 14, 2008 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes, that is what I was getting at. :smile:
  6. Sep 13, 2008 #5
    This looks familiar "yes or no?"
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?