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!

1D Kinematics Again

  1. Oct 7, 2006 #1
    A model rocket is launched straight upward with an initial speed of 70.0 m/s. It accelerates with a constant upward acceleration of 1.00 m/s2 until its engines stop at an altitude of 190 m.

    (a) What is the maximum height reached by the rocket?
    m

    I don't know what I am doing wrong here. I have two pages full of screw ups, haha.

    I tried to find out the final velocity it hits right before it runs out of fuel and I'm stuck

    Using:
    [tex]x = x_0 + v_0 t + (1/2) a t^2[/tex]

    I did 190 = 0 + (70)t + 1/2(1)(t^2)

    I get down to 190 = 70t + .5t^2

    I'm just lost so just some guidance would be nice, I know the steps I'm just making a simple error somewhere or something and I've tried for like 60 minutes, so I figured I'd post.
     
  2. jcsd
  3. Oct 7, 2006 #2
    Last edited: Oct 7, 2006
  4. Oct 7, 2006 #3

    Astronuc

    User Avatar

    Staff: Mentor

    The rocket starts with an initial velocity 70.0 m/s and accelerates at a rate of 1 m/s2 over a distance of 190 m to a greater velocity at which point it stops accelerating (because the motor cuts out = no more thrust) and it starts decelerating with gravity -9.8 m/s2.

    So there are two parts to the problem.

    1. The acceleration phase to 190 m. So solve for a constant acceleration problem over 190 m with vo = 70 m/s, and find the velocity at 190 m.

    2. With the velocity determined in 1) determine the altitude the rocket achieves with that initial velocity at 190 m.

    http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html#mot1
     
  5. Oct 10, 2006 #4
    Thank you, I got the answers using your help.

    A model rocket is launched straight upward with an initial speed of 70.0 m/s. It accelerates with a constant upward acceleration of 1.00 m/s2 until its engines stop at an altitude of 190 m.

    (a) What is the maximum height reached by the rocket?
    455.68 m
    (b) How long after lift-off does the rocket reach its maximum height?
    10.06 s
    (c) How long is the rocket in the air?
    19.876 s
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: 1D Kinematics Again
  1. 1D Kinematics (Replies: 2)

  2. 1D Kinematics (Replies: 5)

  3. 1D kinematics (Replies: 2)

  4. Kinematics in 1D (Replies: 2)

  5. 1D Kinematics (Replies: 10)

Loading...