Are newtons laws of motion useless on earth? There are other external forces acting on objects eg friction?

Answer 1

Yes, there are other forces acting on objects, but Newton's laws say the sum of those forces = mass times acceleration. Still true, just more complicated than HS introductory physics may make you think.
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Answer 2

No, they are valid. For example friction does not invalidate the first law of motion that any object in a state of rest or of uniform motion will continue to remain in that state unless and until acted upon by an external force. So since friction is an external force, it can be accounted for. After accounting for friction, if the change of state of an object cannot be explained, an external hitherto unseen force is brought into reckoning.

So, I don't see any contradiction and feel that the statement was made by one with a less than perfect understanding of the laws.

Answer 3

Most people have a hard time understanding the laws of physics. One of the laws is: For every action there is an equal and opposite reaction. Without this law we would not have the jet airplanes. Another law:with out a force acting on it a mass will not move.Without this law we would not have automobiles. And finally : An object in motion tends to remain so. A car without brakes would cause a great many accidents.
All of these things are things on this earth.

Answer 4

Newtons laws work everywhere! (Well -- maybe not close to or inside a black hole, or if you go 3000 km per second).

You need to include gravity, friction, air resistance, etc. as some of the forces acting on an object. Once you that, the laws work to explain how the object moves.

It's just that the forces from friction and air resistance are complicated, so they usually aren't included in physics problems until after a few years of college.

Answer 5

you do no longer sound stupid. Now.you assert that "Why would desire to there be a 2nd rigidity while the table opposes the item from falling down besides?" yet this opposition easily is that 2nd rigidity. It comes from the electromagnetic rigidity between the molecules of the table. think the table replace into made up of air. Then would it not have been waiting to 'oppose' the item? No. via fact air molecules are no longer rigidly bonded to a minimum of one yet another via the electromagnetic rigidity, in assessment to those of solids. don't be under the impression that a rigidity exists purely while there is a few circulate linked with it. seem at it this way - First the item exerts some rigidity on the table floor(that's via fact gravity is pulling it down). Now this rigidity is positioned on the exterior molecules which in turn positioned it on the indoors molecules. those returned transmit the rigidity until it reaches the backside and is carried all the thank you to the earth's centre(from the place gravity could be meant to act). Now those style of molecules in between push against one yet another via the electromagnetic rigidity, keeping the area between themselves. in the event that they did no longer exert this rigidity, they might all cave in and the item would cave in however the table. this occasion would make it sparkling. think you're enjoying a sport of tug of warfare. each and all the two gamers could be meant to characterize the earth and the item. The pull exerted on the rope stands for gravity. Now, in case you place a brilliant merchandise between yourselves, like a field, it could characterize the table on your subject.It stops the two human beings coming at the same time via fact that's molecules repel one yet another via the electromagnetic rigidity. So the mysterious rigidity which you're puzzled approximately is definitely the electromagnetic rigidity.

Answer 6

Of course Newton's laws are not useless on earth. Where do you think he came up with these laws.....?

Answer 7

They take all forces into account, including friction.