Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find its maximum height and initial velocity

  1. Oct 3, 2004 #1
    Hello i have been able to do 7 out of 8 question on my linear motion questions, but this last question number 8, is proving difficult. I don't know whether the tutor has made a mistake (as the answers are typed at the bottom) so if you could be of help i would be very glad ty.

    I am using s = u.t + 0.5.a.t^2

    and v = U + a.t

    but neither bring up the correct answers:

    8. A pistol pellet is fired vertically upwards and lands back at its firing point
    8 seconds later. Neglecting air resistance, and assuming the acceleration due to gravity is g = 9.81 m/s2 downwards ! find its maximum height and initial velocity.
    [answers: 78.5 m , 39.2 m/s]

    Ty every so much :-)
  2. jcsd
  3. Oct 3, 2004 #2
    Welcome to PF :biggrin:
    The bullet starts with velocity v,slows down due to gravity,and attains v=0 at max height.Then it picks up speed(due to gravity) and reaches down with total velocity v.
    So time taken to attain v=0 is 8/2=4s.
    I plugged this into the eqn and got the given answer.
    Similarly,height reached is when velocity becomes 0,I got the given answer with the eqn you gave.
    I think you tried t=8s.I hope you understood.
    Last edited: Oct 3, 2004
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Find its maximum height and initial velocity
  1. Initial velocity (Replies: 3)