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!

Kinematics in 2d, plane drops an object

  1. Jan 17, 2009 #1
    1. The problem statement, all variables and given/known data
    A certain airplane has a speed of 267.2 km/h and is diving at an angle of θ = 28.0° below the horizontal when the pilot releases a radar decoy (Fig. 4-37). The horizontal distance between the release point and the point where the decoy strikes the ground is d = 777 m. (a) How long is the decoy in the air? (b) How high was the release point?

    2. Relevant equations

    3. The attempt at a solution
    Okay, step one is to find the velocity in the x and y directions, here is my attempt:
    Vy=sin(-28)*267.2= -125.4428016
    Vx=cos(-28)*267.2= 235.9235968

    So we have the following knowns:

    Okay, cool, plenty of information. Let's solve for T first so we can find Dy afterwards:
    Dx=VxT + 1/2Ax(T^2)
    777=(235.9235968)(T) + (1/2)0(T^2)
    777=(235.9235968)(T) + 0

    Now at this point, I went on to solve for Dy, but we're gonna stop here for the following reason: when I submitted my answer for T to the wileyplus online system, it told me my answer was wrong. What did I do wrong? Everything seems to make sense. Please help!
  2. jcsd
  3. Jan 18, 2009 #2


    User Avatar
    Science Advisor

    The speed of the airplane is given in km/hr. You should check for consistency in your units ;)
  4. Jan 18, 2009 #3
    Ah jeez, totally overlooked that. Thanks for the help!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Kinematics in 2d, plane drops an object