Rocket's Max Altitude & Flight Time

AI Thread Summary
The discussion centers on calculating the maximum altitude and total flight time of a weather rocket with specified parameters. The rocket accelerates at 31.0 m/s² for 35 seconds before running out of fuel, and participants emphasize the importance of breaking the problem into two phases: powered ascent and free flight. While some express confusion about incorporating the rocket's mass, others clarify that it is not necessary for this specific kinematic analysis. The key steps involve calculating the height reached during powered flight and then determining the additional height gained during free flight until the rocket reaches its peak. Ultimately, the focus is on applying basic kinematics to solve for the rocket's maximum altitude and total time in the air.
jelder
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A 200kg weather rocket is loaded with 100 kg of fuel and fired straight up. It accelerates upward at 31.0 {\rm m/s^2} for 35.0 s, then runs out of fuel. Ignore any air resistance effects.

I just don't know how to integrate the weight into the problem

known variables (hopefully they are correct this may be where I went wrong)
vi=0m/s
xi=0km
xf=?
a=31.0m/s^2
t=35.0s



What is the rocket's maximum altitude?



How long is the rocket in the air?
 
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Why do you think you need to take the mass into account? I don't think that it's relevant to the question as it makes it much more complicated than just basic kinematics. Actually, the information in the question is set up so you don't have to worry about it.

Think about this question in two pieces: one piece is when the fuel is burning, and the other is after the fuel runs out.

How do you think you can find the height of the rocket at the point where the fuel just runs out?
 

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