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!

Projectile motion

  1. Sep 18, 2007 #1
    some body help me...it is very simple...somebody throws two rocks from the top of a hill, one above the horizontal line and the other rock below the horizontal line, at an angle of 30 degrees for both rocks and the inicial speed is 13m/s for both rocks as well...the quiestion is how far does the rock 1 is from rock two when they both touch the ground..(rock 1 is the one below horizontal line...rock 2 over the hor....line)...wht i do not know is if wheter rock one(going down) has an inicial speed of 6.5m/s or 13m/s....by the way 6.5m/s comes from the inicial vertical velocity= (sin30)(13m/s)...

    probelm.JPG
     
  2. jcsd
  3. Sep 18, 2007 #2
    Try drawing a picture of the problem, it may help you visualize what is going on better.
     
  4. Sep 18, 2007 #3
    i have the picture in my book..just tellme if you know how to calculate the inical speed when a body is thrown downward at an angle of 30 degrees (below the horizontal line) with an initial speed of 13m/s?is it the same speed as the inicial vertical velocity or it is only the inicial speed given..?
     
  5. Sep 18, 2007 #4

    learningphysics

    User Avatar
    Homework Helper

    the initial horizontal speed is 13cos(30). The initial vertical speed is 13sin(-30) = -13sin(30). in other words the initial vertical speed is 13sin(30) downwards.
     
  6. Sep 18, 2007 #5
    i suppose that it is -6.5 then?
     
  7. Sep 18, 2007 #6

    learningphysics

    User Avatar
    Homework Helper

    Yes, the one thrown downward at 30 degrees below the horizontal has initial vertical velocity -6.5m/s.

    The one thrown above has initial vertical velocity 6.5m/s.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Projectile motion
Loading...