What is the correct maximum altitude and flight time calculation for a rocket?

AI Thread Summary
The discussion centers on calculating the maximum altitude and total flight time of a rocket weighing 200 kg with 100 kg of fuel, accelerating at 30 m/s² for 30 seconds. The initial calculations for flight time vary, with one participant suggesting 228 seconds while another argues for 181.69 seconds. The confusion arises from incorrect formula usage in the calculations. After corrections and clarifications, the flight time is confirmed to be approximately 228 seconds. The thread emphasizes the importance of accurate formula application in physics problems.
Coffeepower
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Homework Statement


A 200kg rocket is loaded with 100kg of fuel and fired straight up. It accelerates at 30m/s^2 for 30sec and then runs out of fuel. Ignore any air resistance effects.

a. What is the maximum altitude of the rocket?
b. How long is the rocket in te air?
c. Draw a position vs. time graph of the rocket from launch to impact.

The Attempt at a Solution



http://www.angelfire.com/planet/garciarussellchem/coolpix/

The text says that the answer to (b) is 228sec. I say it is 181.69sec. what happened here?

p.s. Ignore the circled answer for (b) in the figure because it is wrong.
 
Last edited:
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Show how you arrived at your answer. (The image is blank.)
 
http://www.angelfire.com/planet/garciarussellchem/coolpix/

Just updated the image. Try it now.
 
In part of your calculation you use this formula, which is incorrect:
v_f = v_i + 2a\Delta t
 
Thank you. That really helped out.

I got 227.6 = (rounded) 228sec.
 

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