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. Dec 7, 2008 #1
    1. The problem statement, all variables and given/known data

    You throw a baseball to hit a target on the ground 10m from the base of a building 25m in height. (a) With what velocity must you throw the baseball if it is to leave the hand horizontally? (b) with what velocity mut you throw the baseball if it is to leave the hand at a angle of 45 up from the horizontal? (c0 What is the horizontal component of the initial value o the velocity in case (b)?

    2. Relevant equations

    (a) s=ut +1/2at^2
    v=d/t

    (b) i have no clue

    (c) Vx(cos theta)





    3. The attempt at a solution



    (a)s=ut+1/2at^2
    25=0+ 1/2(9.8)t^2
    25= 4.9t^2
    25/4.9=t^2
    t=√5.10
    t=2.26s

    v=d/t
    = 10/2.26s
    =4.42m/s

    (b) i don't know can someone point me in the right direction
     
  2. jcsd
  3. Dec 7, 2008 #2

    LowlyPion

    User Avatar
    Homework Helper

    If it is thrown at 45° then Vx = Vy.

    That means you can take your x and y equations and solve more easiily.

    25 = Vy*t - ½gt²

    10 = Vx*t

    With Vx = Vy and t = 10/V ...
     
  4. Dec 7, 2008 #3
    so its:
    25=4.42(cos45)(t)+0.5(9.8)t^2

    and solve for t

    then use v=d/t

    and find the velocity?
     
  5. Dec 7, 2008 #4

    LowlyPion

    User Avatar
    Homework Helper

    I'd just stick 10/V into the y equation for t and solve for Vx,Vy directly.

    Then Vo = V/sin45 = Vx(√ 2)
     
  6. Dec 7, 2008 #5
    i am confused
     
  7. Dec 7, 2008 #6

    LowlyPion

    User Avatar
    Homework Helper

    Since -25 = Vy*t - ½gt²

    And |Vx| = |Vy| and

    Vx = 10/t

    Then Vy = 10/t or t = 10/Vy

    Hence -25 = Vy*10/Vy - ½*g*(10/Vy)²

    Simplifying 70V² = 100*g = 980

    Vy = Vx = 3.74 m/s

    Vo = 5.29 m/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...