Rocket Problem: Determining the amount of fuel burned

Razor suggests that the simplest solution is often the correct one. In summary, the initial acceleration of the 20,000kg rocket is 15.2 m/s^2 and the mass of fuel burned at an altitude of 5,000m is 6,444.44kg. This is determined by using the equation F=ma and recognizing that the thrust remains constant while the mass of the rocket decreases as fuel is burned.
  • #1
Ockham
14
0
The set up:
A 20,000kg rocket has a motor that generates a thrust of 3x10^5 N.


The problem:
a)What is it's initial Acceleration?

b)At an altitude of 5,000m the rockets acceleration has increased to 6 m/s^2, what mass of fuel has it burned?

Relevant equations:

F = ma

The attempt at a solution:

I found the initial Acceleration to be 5.2 by taking the difference of the thrust and the rockets weight and dividing my the initial mass.

Part two is the one I can't figure out...I don't think the height of the rocket has anything to do with the solution does it?
 
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  • #2
I agree, the altitude is unnecessary. In fact, it's a bit odd because you could calculate the altitude, and I'll bet it's not 5km exactly.
 
  • #3
How do I determine the amount of fuel burned?
 
  • #4
Recall how you calculated the initial acceleration. Why does the acceleration increase? What, in your calculation, will have remained constant?
 
  • #5
OH...thanks. I get it now. The Thrust is constant the only thing that changes is the mass. Which I can solve for.


Thank you!
Ockham
 

FAQ: Rocket Problem: Determining the amount of fuel burned

How do you determine the amount of fuel burned in a rocket?

The amount of fuel burned in a rocket can be determined by measuring the change in the rocket's mass before and after launch. The difference in mass represents the amount of fuel burned during liftoff.

What factors affect the amount of fuel burned in a rocket?

The amount of fuel burned in a rocket is affected by various factors such as the weight of the payload, the distance the rocket needs to travel, and the efficiency of the rocket's engines.

Can the amount of fuel burned be calculated before the launch?

Yes, the amount of fuel burned can be calculated before the launch by using mathematical equations that take into account the factors mentioned above. However, the actual amount of fuel burned may vary slightly due to external factors such as wind resistance.

How does the type of fuel used affect the amount burned in a rocket?

The type of fuel used can greatly affect the amount burned in a rocket. For example, more efficient fuels will result in less fuel being burned for the same amount of thrust. Additionally, the type of fuel can also impact the weight of the rocket, which in turn affects the amount of fuel needed.

How does the amount of fuel burned impact the trajectory of the rocket?

The amount of fuel burned directly affects the trajectory of a rocket. The more fuel burned, the faster the rocket will accelerate and the higher it will go. However, if too much fuel is burned, the rocket may become too heavy and may not reach its intended destination.

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