An object at rest &quot;tends&quot; to stay at rest?

An object at rest "tends" to stay at rest? Rate Topic:

#41 27 November 2011 - 10:01 PM swansont

Shaken, not Stirred

questioning_the_theory, on 27 November 2011 - 08:30 PM, said:

I always thought that with Newton's understanding, he would have stated it more like
"an object's motion remains constant unless acted upon by some force." Since it seems
that it must have been clear to him that "everything" is in motion, there is nothing we
know of that is "at rest".

That's not clear to me. Anyway, whatever you've read about Newton's laws is a translation from Latin.

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#42 27 November 2011 - 11:50 PM bbouch111

Quark

Am I the only person who has a hard time believing that an object in motion tends to stay in motion? If this is true, doesn't that mean a car could never stop moving if it were to start moving? This law stated that an object would stay still unless acted upon by an external source, but he never defined an object in motion. He never set a true definition to the object in motion. Does that mean that all objects are at rest until they are put into motion? That doesn't work because an external force can physically stop an object in motion and put it into a resting state.

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#43 28 November 2011 - 02:26 AM swansont

Shaken, not Stirred

bbouch111, on 27 November 2011 - 11:50 PM, said:

No, you aren't the only one, because there are a number of people who don't understand physics. A car is subject to forces which bring it to rest, which is fully in accordance with Newton's laws. But those forces have to be there to bring it to rest.

Objects that are not subject to accelerations are at rest in their own frame of reference. Motion is always in reference to some frame.

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#44 24 December 2011 - 05:01 AM Samm

Quark

bbouch111, on 27 November 2011 - 11:50 PM, said:

Am I the only person who has a hard time believing that an object in motion tends to stay in motion? If this is true, doesn't that mean a car could never stop moving if it were to start moving?

That would be true if the car was on a frictionless road, driving in a perfect vacuum.