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Physics 11 Net force and Acceleration

  1. Feb 14, 2008 #1
    1. The problem statement, all variables and given/known data
    g=10m/s^2
    A fully loaded Saturn rocket has a mass of 2.92x10^6kg. Its engines have a thrust of 3.34x10^7N.

    a) How much does the rocket weigh. answer 2.92x10^7 N
    b) What is the net force on the rocket when it blasts off? answer 4.2x10^6N
    c) What is the acceleration as it leaves the launch pad? 144m/s^2
    d) What is its speed after 60 seconds? answer 86.4m/s
    e) As the rocket moves away, the engine thrust is constant but the mass decreases - why? What effect does this have on acceleration. answer Fuel is consumed; m decreases, a increases.

    2. Relevant equations

    F=ma P.E. =mgh

    3. The attempt at a solution
    I have no idea how the answer for b) becomes 4.2x10^6N
    Any help would be appreciated.
     
  2. jcsd
  3. Feb 14, 2008 #2
    Part c

    Based on the question I got the mass as 2.92 and the thrust as 33.4. 33.4 to match the exponent for both numbers. The answer I got when F/m=a is 33.4kg by m/s^2/2.92Kg=11.4m/s^2m/s^2. This is obviously wrong. What am I doing wrong?
     
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