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Let's say a particle is moving in a straight with no acceleration in an inertial frame. By Newton's laws we know that the force acting on it must be 0. But my question is, why doesn't uniform velocity effect the net force acting on it?

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    $\begingroup$ Newton's laws are based on observation. I'm not sure if there's a better answer than "because that's how it works". $\endgroup$ – JMac Jul 9 at 10:43
  • $\begingroup$ It would be helpful if you could explain why you think the velocity would have an effect on the net force. Perhaps give us a "thought experiment" or two. $\endgroup$ – garyp Jul 9 at 11:03
  • $\begingroup$ Because let's imagine an isolated space, in which an object is moving with uniform velocity , and hits another object. I can imagine a force being exerted by the moving on the other, after which the momentum gets transferred. $\endgroup$ – NightKruger Jul 9 at 11:06
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I think you are perhaps confusing two different concepts.

Newton's First Law tells us that the net force on an object moving with uniform velocity (relative to an inertial frame) is zero. This is a law based on observation and experiment - whenever we see an object moving with non-uniform velocity, we also find that there is some net force acting on the object.

On the other hand, there are forces that are a function of the velocity of an object - the drag force acting on an object moving in air or in a fluid is one example. But in these cases the object will not move with uniform velocity - unless the drag force is opposed by an equal and opposite force such as gravity, resulting in a zero net force on the object.

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