How velocity builds up in space

In summary, Newton's first law of motion states that an object will remain at rest or at a constant velocity unless acted upon by an external force. This law applies to space, where velocity can build up due to the effects of gravity and the conservation of momentum. If a rocket is shot into outer space, it will continue to travel at the velocity achieved even if the propulsion source is removed. In space, there is no friction to slow down the rocket, so it will continue at a constant velocity unless acted upon by another force. It is also possible to achieve a build-up in velocity by exerting a continuous force on an object in space. However, at high velocities, the laws of Special Relativity take over and Newtonian mechanics may
  • #1
lpbug
19
0
According to Newton's first law of motion: "An object at rest will remain at rest and an object at motion will remain at a constant velocity unless acted upon by an external force."
I was just wondering if this law applies to space; since there are no friction in air and little to no gravity, I was just wondering if velocity could build up in space. For example, I shot a rocket into outer space and the more velocity I add to it the faster it goes and even if I take out the source of propulsion, it'll still travel as fast as I set it without ever slowing down.
Thanks for answering!
 
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  • #2
If you include the spent fuel expelled by the rocket's engine as part of the rocket's mass, there are no external forces, and momentum is conservered. However chemical energy is converted into kinetic energy, most of this into the fuel which ends up with a very high velocity with respect to the rocket engine.
 
  • #3
In general, Newton's laws apply in space as here on earth. gravity, friction, and other forces may vary, but the LAWS remain intact.

"I was just wondering if this law applies to space; since there are no friction in air and little to no gravity, I was just wondering if velocity could build up in space..."

Velocity can build in space due to F = MA and V=AT as a body approaches a planet for example...where gravity exerts a force on the body and the body accelerates. This effect can be ustilized to good effect in space probes where the "slingshot effect" can be used to speed up vehicles.


"For example, I shot a rocket into outer space and the more velocity I add to it the faster it goes and even if I take out the source of propulsion, it'll still travel as fast as I set it without ever slowing down."

If you assume no friction in space then one view is that there are no forces to slow it down. In fact space is curved by gravity in different places,more so near large masses like stars, so over time the rocket will turn and follow gravitational curves a bit,,,if you ignore these, it will retain a constant fixed "straiht line" velocity.

Once the rocket engine is turned off in free space, no friction and no other forces, the rocket will continue at the velocity achieved...it won't slow down nor speed up because there are no additional forces acting...restart the rocket engine...apply a force... acceleration ensures and velocity increases...
 
  • #4
As a matter of fact, in the extremely low friction environmentthe two parts of this law become one. If you put yourself in the Rockets place, with no nearby objects against which to compare yourself, you will find that you're able to tell the difference between "accelerating" and "not accelerating," but the difference between "moving very fast at a constant velocity," "moving very slowly at a constant velocity," and "sitting still" will require you to ask, "compared to what?"

So, moving at a constant velocity literally is remaining at rest.
 
  • #5
Ok... well, so if i keep on exerting force upon the "rocket" I can achieve a build-up in the rocket's velocity right? So it'll keep on going faster and faster... is that correct?
 
  • #6
Yes, that is correct. Without wind resistance, there is no "terminal velocity." As long as you keep pushing, the rocket (or any object) will keep accelerating.
 
  • #7
A semi-related question: Is it possible to get something to stand completely still out in space? I'm not talking about on the lowest level, I know there'll always be some movement there, but larger objects. Would there be anyway to tell if an object didn't move at all, considering everything else in space is moving? Some way to measure an object's kinetic energy perhaps?
 
  • #8
Since velocity can only be measured with respect to other objects, so too, kinetic energy.
 
  • #9
wait but it builds up right? I mean it will buld up like:
i start out 20Mph and slowly i will accelerate to 100mph and keep adding up right?
 
  • #10
lpbug said:
wait but it builds up right? I mean it will buld up like:
i start out 20Mph and slowly i will accelerate to 100mph and keep adding up right?
Hmm, yes.

I think I can see where your going with this...
 
  • #11
...the rules that work at low speed start breaking down at high speed. Special Relativity takes over for Newtonian mechanics.
 

FAQ: How velocity builds up in space

How does an object gain velocity in the vacuum of space?

An object gains velocity in space through the application of a force, either through propulsion from a thruster or the gravitational pull of another object. In the vacuum of space, there is no air resistance to slow down the object, allowing it to continue to accelerate.

What factors affect the velocity of an object in space?

The velocity of an object in space is affected by several factors, including the force applied to the object, the mass of the object, and the presence of other objects with gravitational pull. The direction of the force and the angle of acceleration also play a role in determining the object's velocity.

How does an object's velocity change when it enters a different gravitational field?

When an object enters a different gravitational field, its velocity may change due to the pull of the new object's gravity. The object's velocity may increase or decrease depending on the strength and direction of the gravitational force. The object's trajectory may also be altered.

Can an object's velocity continue to increase indefinitely in space?

No, an object's velocity cannot increase indefinitely in space. The object will eventually reach a maximum velocity known as the escape velocity, which is determined by the mass and gravitational pull of the object it is trying to escape from. Once the object reaches escape velocity, it will continue to travel at a constant speed unless acted upon by another force.

How do astronauts control the velocity of spacecraft in space?

Astronauts can control the velocity of spacecraft in space through the use of thrusters, which provide a force in a specific direction to change the spacecraft's velocity. They can also use gravity assists, which involve using the gravitational pull of other objects to increase or decrease the spacecraft's velocity. Additionally, precise calculations and adjustments are made using computer systems to control the spacecraft's velocity.

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