How Do You Calculate Rocket Acceleration and Altitude After Launch?

[cheerspens]

Homework Statement

A Saturn-Apollo rocket has a mass of 5.40 x 10⁵kg. What is the initial acceleration of the rocket if the thrust at lift off is 7.40 x 10⁶ N?
How high will the rocket rise one minute after launch?

Homework Equations

Fg=mg
F_NET=ma

The Attempt at a Solution

I used Fg=mg, plugging in 5.5 x 10⁵ for m and 9.8 for g to get Fg=5.292 x 10⁶ N.
I then used the F_NET equation as so:
7.4 x 10⁶-5.292 x 10⁶=(5.4 x 10⁵)(a)
And my answer was an acceleration of 3.89m/s².
For the second question I got that the rocket would reach 233.4m one minute after launch.
Is this correct or how is this done correctly? Thanks!

 

[rock.freak667]

Your method is correct, but you did the operations wrong I believe. The thrust after lift off is the resultant force. So you need to add that to the weight and then get the acceleration.