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!

Final velocity help

  1. May 19, 2015 #1
    What will the final velocity of 5.0 g bullet starting from rest if a net force of 45 N is applied over a distance of 0.80 m ?


    2.


    3. i tried to solve it but i don't know of my anwer is correct
    F=ma, F/m=a
    45/.005 kg
    a=9000m/s^-2
    From this formula ( d=1/2at^2) we can say that
    Time= 2d/a and then take under root
    2×0.80/9000 (under root or square root)
    =0.013 sec
    initial velocity (u) =0
    a=v-u/t
    at=v-u
    9000×0.013=v-0
    117+0=v
    answer is 117m/s^-1
     
    Last edited by a moderator: May 19, 2015
  2. jcsd
  3. May 19, 2015 #2
  4. May 19, 2015 #3

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    You get 120m/s if you don't round down to 0.013 seconds.
     
  5. May 19, 2015 #4
    I don't understand what you mean by this. Please tell what does it mean because i am only in 8 grade
     
  6. May 19, 2015 #5
    What CWatters means is that 0,013 s is not the exact value of the time. If you use the exact value, which is t = (2*0,8/9000)^(1/2), you will get a slightly different, more correct answer. I would recommend googleing "significat numbers". :)
     
  7. May 19, 2015 #6
    Thank you very much for your help. I also had the same answer but the problem was that i shortened 0.0133333333333 to 0.013 thats why my answer was 117 and not 120.
     
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: Final velocity help
Loading...