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 projectile motion

  1. Oct 18, 2012 #1
    Stuck on these hw problems.

    1. A ball is launched 60 degrees above the x axis to a helicopter that is 110 feet away and 90 feet high. What is the initial velocity required to reach it?

    I know the equation we have to use is

    90 = viT + .5aT^2

    and that 90 = vi(cos60)T


    2. Another ball is launched with an initial velocity of 38 m/s and lands 29 meters away. Find the two angles that meet this.

    would you use the same equations?
     
  2. jcsd
  3. Oct 18, 2012 #2
    Keep in mind that x and y are separate.
    So you know that in time T the ball must travel 110 feet in the x direction and 90 feet in the y direction.

    Your equations are close, but v_i in the first equation should only be the y component of v_i.
    the second equation is for the x direction, so you should have 110 feet, not 90.

    But otherwise, looks solid. Now, since you have 2 equations and 2 unknowns, you have to solve for one variable and then substitute it into the other equation. (Try solving the second equation for T and going from there)


    Not sure about #2. Seems you have 3 unknowns (y, t and angle).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Help with projectile motion
  1. Projectile Motion help (Replies: 4)

  2. Projectile Motion Help (Replies: 2)

Loading...