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!

Homework Help: Projectile Motion ball velocity

  1. Feb 6, 2012 #1
    1. The problem statement, all variables and given/known data
    A physics student on Planet Exidor throws a ball, and it follows the parabolic trajectory shown. The ball's position is shown at 1.00 s intervals until t=3.00 s. At t=1.00 s, the ball's velocity is v=(2.73i+1.78j) m/s. Determine the ball's velocity at t=0.00 s. (Enter your answer in component form. Input the x-component first, followed by the y-component.)
    http://capa.physics.mcmaster.ca/figures/kn/Graph06/kn-pic0608.png [Broken]

    2. Relevant equations
    I know that v0x=vcos∅ and v0y=vsin∅

    3. The attempt at a solution
    I'm not sure how to begin without being provided with the launch angle. I tried to find the angle using the given velocities (at t=1 s), using tan-1= vy/vx=1.78/2.73, which gave me 33.1. But this angle, at t=1, will not be the same as the launch angle, right?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Feb 6, 2012 #2
    From the diagram you know that the velocity in the y direction is 0 at t=2
    You can you this to work out the acceleration due to gravity g from which you can find the y component of velocity at t=0
  4. Feb 6, 2012 #3
    I'm not sure what you meant about working out the acceleration due to gravity, but I used the fact that Vy =1.78 at 1 sec to find the y component of velocity at t=0. So, I did V0y=Vy-at
    =1.78- (-9.8) (1)=11.58 m/s
    Am i on the right track? How would i go about finding the acceleration in the x direction to do the same for v0x?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook