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KWOOOSH OP t1_jazrqcu wrote

Reply to comment by HoldingTheFire in How is it that objects in equilibrium stay in motion at constant velocity? by KWOOOSH

>object can travel at constant velocity without any added force. It in fact it will take a force to slow it.

I understand that the forces acting on the object opposite of its motions causes it to decelerate. With your space example, I know if you give something an initial push, it will keep moving forever unless another net force acts on it. But how does it keep moving forward? I know that something must act on the object for it to change acceleration, but how can it move in the first place without any net force. It intuitively makes sense to me that when net force = 0, then that means no motion, but how can an object move at all when net force =0? Is that just inertia by definition?

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Thanks for the reply, and sorry if my original question was unclear.

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HoldingTheFire t1_jaztfr6 wrote

Force changes acceleration. So you need a force to accelerate an object from rest to a constant velocity. But at a constant velocity acceleration is zero and so is the force. There in energy in the object, energy from the initial force used to accelerate it, but it doesn't cost energy to keep moving.

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adam_vink t1_jb10yht wrote

Yes, that is just inertia by definition (see below definition from dictionary.com) "the property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force."

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