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!

Physics 11 Net force and Acceleration

  1. Feb 14, 2008 #1
    1. The problem statement, all variables and given/known data
    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?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook