Question relating Newton's First Law of motion

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Discussion Overview

The discussion revolves around Newton's First Law of motion, particularly in the context of a space shuttle moving in outer space without the influence of gravity. Participants explore the implications of stopping the engine and the resulting motion of the shuttle, addressing concepts of force, friction, and motion in a vacuum.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the motion of a space shuttle when its engine stops, questioning whether it would eventually come to a stop due to the absence of forward force.
  • Another participant argues that the intuition of an object stopping when a force is removed is misleading, emphasizing that in the absence of any forces, an object will continue moving at a constant velocity indefinitely.
  • A participant highlights the difference between conditions on Earth, where friction is present, and those in space, where an object can maintain its speed without external forces acting upon it.
  • Discussion includes the idea that satellites in orbit experience minimal friction and require occasional boosts to maintain their position, as they are still affected by Earth's gravity.
  • One participant uses an analogy involving a rock on a string to illustrate that when a force is removed, the object will continue in a straight line at the velocity it had prior to the force being removed.

Areas of Agreement / Disagreement

Participants generally agree on the principle that an object in space will continue moving at a constant velocity when no forces act upon it. However, there are differing views on the implications of this principle, particularly regarding the effects of gravity and friction in practical scenarios.

Contextual Notes

Some participants mention the complexities of real-world conditions, such as the presence of gravitational forces and friction, which can affect motion differently than the idealized scenarios discussed. There is also mention of the limitations of achieving a true vacuum in practical experiments.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those exploring classical mechanics and the implications of Newton's laws in different environments.

ehabmozart
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Hi there! I kept on reading my textbook and i found one simple confusion in Newton's First law of motion. I want to consider a situation where a space shuttle is moving in the outerspace (assume there is no gravity) under the influence of the engines. What will happen when the engine stops functioning? It is given that the space shuttle will move with a constant velocity. Now, my opinion would be that there was an initial forward force given by the engine, no it is taken off. Is is like pulling the space shuttle. So it ultimately must end up by a stop! This is confusing me. I would really be thankful to whoever helps me in clarifying my confusion. Thanks in advance. I need elaborate answers if u please :)
 
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The intuition that once you stop the force the object will stop is an illusion produced
by the fact that we grow up in an environment where there is friction everywhere. When we stop pushing an object, it may only move a short distance before friction slows it down to a stop. But friction is also a force. If no force at all, including friction, acts on an object, it will move with a constant velocity forever. The ancient people, even the most educated, believed the idea that seems like common sense but is incorrect -- until Galileo figured out the real answer in the 1600s.
 
space is a fun place to do physics because we are allowed to make up situations that we normally couldn't do on earth.

So let's say you are going in your shuttle off Earth into space and at t=20 your engine turns off, and you get past Earth's gravity, you are in free floating space. you could then just keep on going that same speed for ever and ever until you bumped into something, or near something real big. (I think we have satelights pointed at us sending information that use no fuel to keep on going. Because there is no need)

Thinking it would slow down is common sense nowadaysz because if your rolling down the street on a scooter eventually your going to slow down. There are so many different frictions to think about when on a scooter that we take for granted. The fact that there is air that is trying to get around us slows us down, plus friction between the wheel and the ground, and then the wheel bearing.
 
stoner420 said:
space is a fun place to do physics because we are allowed to make up situations that we normally couldn't do on earth.

yup it sure is we can only sort of create the conditions of Newtons first law of every action has an equal and opposite reaction

At NASA they use smooth floors and have air cusioned units that will glide over the surface with a minimal amount of friction its a very good approximation :)

So let's say you are going in your shuttle off Earth into space and at t=20 your engine turns off, and you get past Earth's gravity, you are in free floating space. you could then just keep on going that same speed for ever and ever until you bumped into something, or near something real big. (I think we have satelights pointed at us sending information that use no fuel to keep on going. Because there is no need)

very difficult to get away from the effects of Earth's gravity. You much be a VERY long way away. Remember that even in orbit satellites, shuttle and its astronauts are in a constant state of freefall due to gravity

Satellites do have small rocket thrusters ( usually just gas exhausts) these are there to periodically boost the satellite's orbit. Most satellites (in lower Earth orbit regions) are not that far above the Earth's atmosphere and the small amount of resistance from that and loss of orbital velocity means they do slowly loose orbital height and need the occassional boost to get them back in position.

The life of the satellite comes to an end when there is no more propellant on the satellite to do the boosts in orbit and then they are on that inevidable spiral back into the atmosphere and burn up

Dave
 
When you stop accelerating an object, it will continue to move at the velocity it had before.
For example, say I had a rock and attached a string to it, then went and spun the rock with the string (Think David and Goliath),after a while the string snapped and ceased to pull on the rock, the rock will fly out tangent to the circular trajectory it used to be on.
 

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