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!

Projectile motion

  1. Apr 25, 2013 #1
    1. The problem statement, all variables and given/known data

    A particle is projected at 30 m/s from the foot of a plane which is inclined at 30o to the horizontal. The particle hits the plane at an angle perpendicular to the plane.
    Find the value of the angle of projection θ and the time taken to reach there.

    2. Relevant equations

    x=30tcosθ , and y=30tsinθ-5t^2 , where (x,y) are the coordinates of the point of impact and θ is the angle of projection, inclined with the horizontal.

    3. The attempt at a solution

    Here is a diagram: http://i.imgur.com/FfTwTD7.png
    So if the projected particle hits the hill at 90o then y/x=1/√3 and the velocity will be at 120o to the horizontal so y'/x'=-√3
    I solved these two equations simultaneously and I got θ=-60 but this looks wrong because it doesn't make sense.
    Please help :)
    Last edited: Apr 25, 2013
  2. jcsd
  3. Apr 25, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    hi |mathematix|! :smile:
    shouldn't |y'| be larger than |x'| ? :confused:
  4. Apr 25, 2013 #3
    Yes, I fixed it :(
  5. Apr 25, 2013 #4


    User Avatar
    Science Advisor
    Homework Helper

    is your answer ok now? :confused:

    if not, show us your full working, so we can see what went wrong :smile:
  6. Apr 25, 2013 #5
    I did the working using the correct values but I got -60 degree for theta. I can't post the full solution now because it would take time and I have to study english now so I will re do it and see if I get a better answer.
    I basically substituted the equations of motion into y/x=1/√3 and y'/x'=-√3 and then solved them simultaneously, found theta and substituted back to find the time, is that the correct approach?
  7. Apr 25, 2013 #6


    User Avatar
    Science Advisor
    Homework Helper

    yes! :smile:
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: Projectile motion
  1. Projectile motion (Replies: 2)

  2. Projectile Motion (Replies: 1)