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!

Help with Forces?

  1. Sep 9, 2012 #1
    An airplane has 1.50x10³ m to accelerate to a speed of 62.0 m/s to take off. If it experiences 15,000N of friction, calculate the thrust of the engines.

    d=1.50x10³ m
    vi=0 m/s
    vf=62.0 m/s
    Ff=15,000N

    v²=u²+2ad
    62²=0+2(1.50x10³)a
    a=1.2813 m/s²

    I think I'm supposed to find the applied force, but I don't know what to do next since I can't find the mass of the airplane.

    A 4.5kg axe comes to a stop in a tree from 25 m/s. How much force did the tree exert on the axe?

    I couldn't come up with anything for this one:

    u=25 m/s
    v=0 m/s
    m=4.5 kg

    ANY HELP IS MUCH APPRECIATED!
     
    Last edited: Sep 9, 2012
  2. jcsd
  3. Sep 9, 2012 #2

    gneill

    User Avatar

    Staff: Mentor

    Both questions are missing critical information that would be needed to calculate a numerical answer. Thus the best you can do is to derive symbolic results with the missing information in the form of a variable. In the first case the missing information is the airplane's mass. In the second it's the depth of penetration of the axe into the tree (or perhaps the time for the axe head to come to rest).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Help with Forces?
  1. Forces Help (Replies: 1)

  2. Force help? (Replies: 1)

  3. Help with forces (Replies: 2)

  4. Forces HELP (Replies: 3)

  5. Forces help (Replies: 7)

Loading...