BRAINY QUESTION

[SUBHAJITRAHUL]

SUPPOSE WE DRAW A LINE ON EARTH SURFACE,IT IS CALLED STRAIGHT LINE,,BUT MY QUESTION IS EARTH IS ROUND SO WHEN WE DRAW THE STRAIGHT LINE ,IS THAT LINE CALLED STRAIGHT OR CURVED?
IF CURVED THEN WE HAVE NO CONCEPT OF STRAIGHT LINE,WHY?
AND THE MAIN FACT IS THE NEWTON'S FIRST LAW IS WRONG...??????

[Old_Geezer]

It is my suspicion that you are not as new here as you appear to be.

[Baldric]

Homework by the look of it!

[SUBHAJITRAHUL]

no,no connection with Newton's 1

[ChuckFickens]

I'd love to know how the conclusion was made that the fact a straight line drawn on the Earth's surface isn't really straight makes Newtons first law incorrect.

[boxtops]

Strange post for a new ABer, is it not?

[ZedBloke]

so please explain your statement that Newtons first law is wrong!

[SUBHAJITRAHUL]

no it is not strange post at all

[magsmay]

It isn't a strange post at all. Early Victorian Surveyors had this problem in Canada when trying to survey and divide the land in straight lines - as the earth has a curvature all straight lines north to south invariably get closer together and would eventually meet at the north pole. Because of this the Surveyors had to add Correction Lines to their surveys (google it). A straight line draw on a piece of paper is in fact straight as it is on a moveable medium but a straight line drawn in the earth -if it was possible to draw a chalk mark in a straight line for a couple of miles -would not be straight, but curved.

[Arksided]

cor blimey the Earth is round... surely that'd be on the news. orb shaped or spherical maybe or even football shaped to six years old young ones.

look at the lines between posts is that straight or wonky? it all depends on ones perspective looking at it.

[Prudie]

Your original premise is wrong because anything drawn on a curved surface is not straight when looked at in 3 dimensions. On a piece of paper, which is 2-dimensional, your line is straight (ie 2 dimensional) but drawn on a ball, for example, it's 3 dimensional. It's really the syntax of 'straight' that confuses the issue. I didn't do physics so I don't what Newton's 1st law is.

[ChuckFickens]

Newtons 1st is basically if an object has no force applied to it then it's velocity remains constant (either at rest, or in motion)

[shoota]

According to Euclid it is impossible to draw a line anyway.

[Prudie]

OK well as a drawn line remains constant and is not an object that has any force applied to it I don't see any connection with that law that disproves it (which is hardly surprising).

[vascop]

//Newtons 1st is basically if an object has no force applied to it then it's velocity remains constant (either at rest, or in motion)//
moves at constant speed in a STRAIGHT line, as I recall.

To address the original question: A line on the earth's surface is a good approximation to a straight line as long as it's not too long.

[ChuckFickens]

"moves at constant speed in a STRAIGHT line, as I recall."

Errm, velocity is a vector based measurement, as such a constant velocity is a consent direction by definition, a direction change means the velocity is not constant.

[vascop]

That's exactly my point!! Because not everybody understands the difference between velocity and speed it is sometimes clearer to say " at constant speed in a straight line" and then it also links well to the initial post.

[vascop]

@original poster
Newton's law is not wrong, because bodies moving in the vicinity of the earth ARE being acted on by forces and so do not travel in straight lines.

[ChuckFickens]

OK fair point...to my mind saying constant velocity means a constant speed in a constant direction, but I agree not everyone would recognise the subtle differences between speed and velocity.

[vascop]

//to my mind saying constant velocity means a constant speed in a constant direction//
and to me, but velocity and speed are used colloquially to mean the same thing and so this can lead to confusion. Not everyone understands the difference between scalars and vectors.

[ChuckFickens]

You'd like to hope that anyone making a relevant comment on the subject in the science section would know the difference though :)

If nothing else I hope this discussion has caused those that don't know the difference to learn it. (although the fact that many don't know the difference saddens me, I learnt this at about 11 years old!)