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!

How to incorporate the initial vellocity

  1. Oct 26, 2003 #1
    I'm having difficulty with the following problem: What is the average force exerted by a shot-putter on a 7.0 kg shot if the shot is moved through a distance of 2.8 m and is released with a speed of 13 m/s.

    I know that I have to use the formula F=ma. The mass is obviously 7.0 kg, but I don't know how to find the horizontal component of the acceleration of the shot. I don't know how to incorporate the initial vellocity and the distance the shot travels. I would appreciate any help. Thanks.
     
  2. jcsd
  3. Oct 26, 2003 #2

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    Use the formula:

    v2 = u2 + 2as
     
    Last edited: Oct 26, 2003
  4. Oct 26, 2003 #3
    what do the variables stand for?
     
  5. Oct 26, 2003 #4

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    v is final velocity (13ms-1), u is initial velocity (assume this to be zero), a is accleration, s is displacement (distance).
     
  6. Oct 26, 2003 #5
    ok, so that gives an acceleration of 2.32m/s^2. But it doesn't make sense that this would be the acceleration to plug into the formula F=ma. I know that the correct answer to the problem is 210 N.
     
  7. Oct 26, 2003 #6

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    Show me your workings, using the above equations I got an answer of 211.25 N (210 N if I'd rounded the accleration to 3 ms-2).
     
    Last edited: Oct 26, 2003
  8. Oct 26, 2003 #7
    I got it! I've been making such a dumb mistake. When I used v^2=u^2 + 2as, I kept forgetting to square the 13! Now i'm getting the right answer. Thanks a lot for helping me out here.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: How to incorporate the initial vellocity
Loading...