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Homework Help: Having trouble finding trajectory of a small rocket

  1. May 23, 2012 #1
    1. The problem statement, all variables and given/known data

    So we launched small rockets on our last day, but have a week to turn in the homework based on the launch, but seeing as we aren't allowed back in school I cant ask questions im lost. We havent dealt with anything remotely related to trajectory since the beginning of fall. I'm confident in doing the math needed, I just need help remembering some formulas. some outstanding questions are-

    * Magnitude of the 2 main forces acting on the rocket ( thrust and gravity)
    * average acceleration
    * final velocity
    * initial velocity when rocket enters coasting phase

    the only data we collected at the launch was the angle of the flight path and we timed the rockets path from ignition to the apex of flight. I have no idea how to get the velocity or acceleration from that.

    if you want my numbers, M of rocket+engine = 37.6 grams, M of Engine = 19.1 grams, M of Rocket = 18.5 grams, flight time to apex = 4.8 Sec, Height angle was 69 degrees measured 200 meters from the launch position. thats all the data i have. THANK YOU!

    2. Relevant equations
    like I said, its been a while and all im really looking for is the relevant equations I need to solve the problems. We use basic algebraic equations. i remember a=v/t, v=d/t and thats all i remember.

    3. The attempt at a solution

    (Tan68) * 200= h
    h= 408.01 meters
    v= 408.01/ 4.8
    v=85.003 m/s
    a= 85.003/ 4.8
    a= 17.709 m/s/s

    (Magnitude of thrust)
    would that be 5.03 * 37.6 = 189.128 N
    (magnitude of gravity)
    would that be 9.8*37.6 = 368.48 N
    if so, how would the rocket fly seeing as the magnitude of gravity is > than magnitude of thrust?
  2. jcsd
  3. May 23, 2012 #2
    This is the actual worksheet that i have to fill out if you want to take a look at that

    Attached Files:

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