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 Question

  1. Oct 11, 2011 #1
    1. The problem statement, all variables and given/known data
    A ball is thrown horizontally with speed u from a height of 20m. It hits the ground with a speed 3u. Find the value of u, and the angle at which the ball strikes the ground.


    2. Relevant equations
    The equations of motion.

    3. The attempt at a solution
    I know that I must deal separately with the horizontal and vertical components of the motion.
    I have worked out that the final vertical velocity will be 19.8m/s but I don't where to go next to find u.
     
  2. jcsd
  3. Oct 11, 2011 #2

    gneill

    User Avatar

    Staff: Mentor

    Write an expression for the speed at which it hits the ground. Set it equal to the required condition.
     
  4. Oct 11, 2011 #3
    I have realised that I now have a triangle where the x component is u, y component is 19.8 and the hypotenuse is 3u. So I could easily work out u and then the angle by using simple trig.

    Is this correct?
     
  5. Oct 11, 2011 #4

    gneill

    User Avatar

    Staff: Mentor

    Looks good! Perhaps consider using Pythagoras.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Projectile Motion Question
Loading...