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!

I'm pretty sure I'm doing this right . . .

  1. Sep 23, 2010 #1
    1. The problem statement, all variables and given/known data

    A turtle crawls along a straight line, which we will call the x-axis with the positive direction to the right. The equation for the turtle's position as a function of time is
    x(t)=50.0 cm+(2.00cm/s)t-(0.0625 cm/s^2)t^2

    At what time t will the turtle be 10 cm from his initial position for the 1st, 2nd, and 3rd times

    2. Relevant equations

    s(x)= r + v(t) - gt^2

    3. The attempt at a solution

    I have solved already for the first and second times for 6.2 and 25.8. I also figure that it takes 32 seconds to reach the initial point. My reasoning would be 32+6.2 giving me 38.2, but that seems to be wrong. Any help please.
     
  2. jcsd
  3. Sep 23, 2010 #2

    Delphi51

    User Avatar
    Homework Helper

    I don't get the 38.2. Recommend you graph
    y = 2t-0.0625*t^2
    and see when it is 10 or -10.
    Then solve -0.0625*t^2 + 2t -10 = 0
    and -0.0625*t^2 + 2t +10 = 0
    to get the answers more precisely.
     
  4. Sep 23, 2010 #3
    Yeah, I got it. Thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook