Rocket acceleration after lauch and during flight

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Discussion Overview

The discussion centers around the acceleration of rockets during launch and flight, exploring how fuel consumption affects acceleration, the role of gravity, and the dynamics involved in both ascent and descent phases. The conversation includes theoretical considerations and practical implications related to rocket motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a rocket continues to accelerate during flight or if it only accelerates during launch, noting that gravity affects its speed.
  • Another participant suggests that a rocket will keep accelerating until it runs out of fuel, after which gravity will dominate.
  • A participant states that once the fuel is spent, the only acceleration acting on the rocket is gravity, which is directed downward at 9.8 m/s².
  • It is proposed that while a rocket is burning fuel, it can achieve a net upward acceleration greater than gravity, but after fuel depletion, gravity will slow it down unless escape velocity is reached.
  • One participant clarifies that positive acceleration occurs as long as engine force exceeds gravitational force, and highlights that slowing down is also a form of acceleration.
  • A question is raised about the acceleration of a rocket during its return to land, suggesting it may exceed 9.81 m/s².
  • Another participant counters that due to atmospheric friction, the rocket's acceleration during descent will be less than 9.81 m/s², despite potentially high velocities.

Areas of Agreement / Disagreement

Participants express varying views on the conditions under which a rocket accelerates or decelerates, particularly regarding the effects of fuel consumption and gravity. There is no consensus on the specifics of acceleration during ascent and descent phases.

Contextual Notes

Some statements rely on assumptions about fuel supply management and the effects of atmospheric conditions, which may not be universally applicable. The discussion also highlights the distinction between acceleration and velocity, which may lead to confusion.

MIA6
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I know mostly that a rocket has acceleration when it is being launched, but does it still keep acceleration when it continues to fly? because my teacher said when this rocket goes up, the speed is decelerating due to gravity. Does this situation only for the rocket that doesn't have acceleration meanwhile, or to the rocket that still keeps acceleration,but i think if a rocket has an acceleration, then it won't be slowed down by gravity.. Hope you can help me out, thanks.
 
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It depends on how the fuel supply is handles. A simple rocket will keep accelerating until it runs out of fuel. Then gravity takes over.
 
Once the fuel is spent the acceleration (neglecting air resistance and curvature of earth) must be 9.8 m/s^2 directed downward.
 
When a rocket is going out of the atmosphere, let's say, it's burning fuel is causing a bigger upward acceleration, than gravity's downward acceleration. So, the rocket has a net upward acceleration.

After the fuel is spent, the only acceleration will be gravity's, and gravity will start to slow it down. If the rocket reached a velocity greater than or equal to what is called the escape velocity, gravity will not be able to pull it back to the planet. Gravity will still slow it down, it just won't be able to make the rocket reverse direction.
 
As everyone has already stated, the rocket will have a positive acceleration for as long as the engine force exceeds 1g. Below that power, a negative acceleration is in effect. (This is assuming an Earth-based launch.)
Some confusion arises in non-scientists sometimes because not everyone realizes that slowing down is also an acceleration, or that a change of direction at constant speed also is.
 
when a rocket wants to return to the land, does it also have acceleration when it returns? it may be probably bigger than 9.81
 
Due to friction, its going to be less than 9.81. The air will slow down the rocket and heat it up. It might come in very fast at Mach 10, but that's velocity, not acceleration. Its going to slow down slower than 9.81 m/s/s.
 

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