really basic physics question - what am I missing

[Brian Ashton]

This is the question:

A person is moving for 2 minutes with a constant speed 4 m/s would cross a distance of?

Ok so moving at 4m/s and 2mins equals 120s. Therefore 4m/s X 120s = 480m

The answer on the test was 240m

So what did I miss.

[Dave Richards]

Whoever wrote the answer key is the one who missed something. You should argue the point or get the instructor to show you why 480m is incorrect.

[Dan Hintz]

Whoever wrote the answer key is the one who missed something. You should argue the point or get the instructor to show you why 480m is incorrect.

Agreed... anytime my step-daughter comes home upset about a test (especially the sciences), I know it's time to check the work. On one test alone, I found 3 grading errors, which raised her an entire letter grade.

Answer keys can be wrong, and so can the teachers.

[Brian Ashton]

Ya I figured so but I tend to give benefit of doubt. It was a test question on a teachers resource site for making up exams. For some reason no ones picked up on it - so I though I was having a brain fart moment...

[Ian Moone]

What medium are they moving at a constant speed of 4 meters per second in?

For example - moving upstream at 4m/second, in a river flowing downstream at 2 meters per second - would equal a "speed over ground" of only 2 meters per second!

This tripped up even the best physicists including Albert Einstein.... (who was dead WRONG about e=mc^2) purely because for his 21 equation proof of e=mc^2 - he relied upon the work of Mitchellson Morley in their light speed experiment which was "fundamentally flawed" in that it split light beams thru half silvered mirrors and then returned them along their own pathway with 100% mirrors to the inter-ferometer to measure the speed of light!.

What they were trying to discern was whether their is an ether of space and of so whether (like a river) it is in motion in relation to the rotation of the earth and its passage thru space about the sun!.

Well - like boats in a river headed to the sea - if you send identical boats both upstream (against the 2m/second current) and downstream (with the 2 meters/second current) each will cover much different distances, due to different total "speeds over ground".

What Mitchellson Morley and Einstein over looked was - if you return those same boats along their same route - the effect of the 2 meter per second current of the moving river is cancelled out - so in effect any effect of a moving space ether or indeed even its very existence was cancelled out in the flawed experimental design of Mitchelson Morelys light speed experiment - when they employed the use of 100% silvered mirrors to return their light beams along their own path to the inter-ferometer!.

Its quite clear in a diagram of the experiment!.



As a result Mitchellson Morley (wrongly) concluded that the speed of light must be constant and traveled at approx 3 x 10^8 meters/per second and Einstein compounded this error when he asserted that e=mc^2.

The facts are Einsteins paper on special relativity was never peer reviewed before being published - or it never would have been published.

The genius Einstein was considered to be without peer after he won his Nobel physics prize for his peer reviewed paper on the photo electric effect!.

However there is a fundamental mathematical error in special relativity that ANY year 9 Math student who paid attention in class should be able to recognize.

Ask most folks the square root of 4 and you will get many who answer 2!

And they would be correct - as was Einstein.

The year 9 math student however who paid attention in class would tell you there are two answers to the question +ve 2 & -v 2 - because any negative integer when squared always yields a positive result!.

What in essence this means (in e=mc^2) is that the SAME photon of light - can travel both +ve (west) at 3 x 10^8 m/second & also -ve (east) at 3 x 10^8 m/second & satisfy the equation e=mc^2!

This is clearly non - sensible and "a mathematics no no" - in that the same photon of light cannot be traveling in 2 opposite directions at the same speed at the same time!

In fact it is a "paradoxical outcome" - which has always been the clue - "there's a major problem in physics". In Einsteins case it was referred to as "the twin paradox" (google it)!

A paradoxical outcome always yields from a false premise & for those unfamiliar, in simple form it looks like this:-

Premise 1. All dogs have 4 legs!
Premise 2 All 4 legged animals are Cats!

Therefore:-

All cats are dogs
or
All dogs are cats!

Which is clearly paradoxical.

And results from false premise 2 = all 4 legged animals are cats

Well Micthelson Morleys premise that there is no ether of space or if there is, it has no motion & thus the speed of light is constant is erroneous - it's a false premise, and results from experimental design error (in returning light beams against their direction of travel back to the inter-ferometer by use of 100% silvered mirrors that clearly as the river / speedboats example - cancels out any effect of the motion in the river running to the sea) or in this case the existence of space ether and any effect upon the speed of light!


Mathematically, there is ONLY one velocity/speed - for the speed of light - that makes e=mc^2 correct - and that is - C=Infinity!

The speed of light is infinite (infinitely fast or equally infinitely slow) because infinity squared = ? Yes Infinity - no messy square root of squares!

E=MC^2 ONLY if the speed of light isn't constant - it is infinite!

So...

Is the question wrong

or

Is it in fact correct IF there is an ether of space, and it too is traveling in the opposite direction the person is moving, at 2m/second - then the resultant speed over ground of the person moving at 4m/second is ONLY 2 meters per second!.

Perhaps the physics question & answer is actually correct?

Perhaps the question encompasses experimental design error or overlooks the negative integer aspect of the ethe rof space in which the person os moving is moving in the opposite direction at half their resultant speed over ground?

Maybe submit that one to the Physics teach and watch their face drain pale and go all grey!

When the teach told me to "further my physics education" it was usually to detention on a bench outside the headmasters office for being disruptive in class.

Mostly it was coz I accept nothing ta face value and question everything!

Sadly I was the ONLY student could tell that Einstein was actually an idiot!.

Well me and Einsteins own professor Dr Hendrick Lorentz, who never got to peer review his physics student Albert Einsteins special relativity paper before it was published & always referred to it in mock derision as "Einsteins Theory" - because it was mathematically incorrect & he knew it.

YMMV = Your Mileage (per second?) May Vary! LOL

[Wade Lippman]

Well Micthelson Morleys premise that there is no ether of space or if there is, it has no motion & thus the speed of light is constant is erroneous - it's a false premise, and results from experimental design error (in returning light beams against their direction of travel back to the inter-ferometer by use of 100% silvered mirrors that clearly as the river / speedboats example - cancels out any effect of the motion in the river running to the sea) or in this case the existence of space ether and any effect upon the speed of light!

This is a safe environment to be in when your meds are failing; no one here will judge you. But please try to spell the big words correctly.

[Ian Moone]

The spelling Nazi's, are out in full force I see.

Michelson, A.A. and Morley

I am more interested in the actual physics & math than the spelling - your mileage may vary.

Its OK if you don't understand it, not everyone does.

If the spelling is important for you, feel free to edit it.

As long as your med's aren't working for you either.

[Prashun Patel]

Fred Flintstone may take a minute to rev up his feet. So even though he's moving them at 4m/s, he's not generating forward momentum until 1 min in.

[Malcolm McLeod]

...Michelson, A.A. and Morley...

They make chisels. Pretty good ones too, if I recall. ...Right?

[Rick Potter]

Simple answer........this question was taken from a 'Common Core' math book.

[Dave Anderson NH]

Errors are not unusual when elementary and middle school teachers with no scientific background try to teach what they don't understand or write a test for their students. My youngest sister has a BSEE and a MS in computer science. Her husband has a Phd in physics. About 15 years ago when my youngest niece brought home a 5th grade enrichment physics program the school was starting, the text had "weight" as the unit in multiple locations where "mass" should have been used. Contact with the teacher, the authors of the program (consultants with connections), and the Principal all failed to make the miscreants understand the difference between weight and mass. Efforts by a neighbor who is a Worcester Polytech physics professor, and another neighbor, a NASA astronaut similarly failed in getting the program changed. The net result was my sister and BIL refusing to let my niece take part in a program incorrectly teaching some of the most basic concepts. It was their only recourse given the intransigence of the school administration. I'm sure similar horror stories occur elsewhere. Most up and coming teachers avoid all science classes as too difficult.

[Mark Blatter]

Errors are not unusual when elementary and middle school teachers with no scientific background try to teach what they don't understand or write a test for their students. My youngest sister has a BSEE and a MS in computer science. Her husband has a Phd in physics. About 15 years ago when my youngest niece brought home a 5th grade enrichment physics program the school was starting, the text had "weight" as the unit in multiple locations where "mass" should have been used. Contact with the teacher, the authors of the program (consultants with connections), and the Principal all failed to make the miscreants understand the difference between weight and mass. Efforts by a neighbor who is a Worcester Polytech physics professor, and another neighbor, a NASA astronaut similarly failed in getting the program changed. The net result was my sister and BIL refusing to let my niece take part in a program incorrectly teaching some of the most basic concepts. It was their only recourse given the intransigence of the school administration. I'm sure similar horror stories occur elsewhere. Most up and coming teachers avoid all science classes as too difficult.

Dave, My experience is many, but not all, teachers do not like to be corrected. Administrators are worse. They have no incentive to be correct, or to correct their mistakes.

[John Stankus]

Errors are not uncommon in teaching materials. Solutions manuals are particularly notorious for having errors. They get subbed out to a graduate student or another professor, who has to solve all the problems in the textbook. That's a lot to do and errors can creep in. Most publishers don't have a good process (at least in my experience ) in catching those errors (someone would have to rework all those problems). I have seen it in most of the textbooks I teach out of, unfortunately.

I actually appreciate my students catching my errors. It reinforces the need to check your work, even for someone who has been a scientist for over 30 years.

As for the rant against Einstein... If it was truly flawed, there would be a gaggle of physicists vying to prove it wrong to make their name. There have been many experimental test of relativity that have been successful. The results of its calculations are necessary for for a range of technologies from quantum electrodynamics to the GPS system. What Einstein got wrong, actually was that he did not believe in quantum mechanics, but that is another story.

It may be apocryphal, but the story I heard about why Einstein won the Nobel prize for the photoelectric effect (an observation critical to the foundation of quantum mechanics), was that in his divorce from his first wife, she stipulated that she get half of the Nobel prize money if he would win it for relativity... so the Swedish Academy awarded it for photoelectric effect.

John

[Wade Lippman]

It may be apocryphal, but the story I heard about why Einstein won the Nobel prize for the photoelectric effect (an observation critical to the foundation of quantum mechanics), was that in his divorce from his first wife, she stipulated that she get half of the Nobel prize money if he would win it for relativity... so the Swedish Academy awarded it for photoelectric effect.

Naw, relativity was still extremely controversial and it would have been risky to give a Nobel for it; but it was recognized that he deserved a Nobel, so he got it for the photoelectric effect instead.
http://discovermagazine.com/2006/sep...n-nobel-prize/
The Nobel committee didn't really care for him; they weren't about to help him swindle his ex.

In 1972 I had a Math professor who said that Einstein was not particularly good at math. When he was at the IAS he would frequently stop by the Math Faculty Lounge and ask for help; he intuitively knew certain equations were true, but didn't know how to prove it. Never-the-less, I am sure relativity has been gone over with a fine tooth comb many times and math errors would have been picked up 100 ago.

Errors are not unusual when elementary and middle school teachers with no scientific background try to teach what they don't understand

In AP US history my son was assigned to make up a recruiting poster for the Union in 1862. He wanted to make it about fighting slavery, but I explained that in 1862 almost no one was willing to die to fight slavery; the poster had to be about preserving the nation. He got a C because he didn't make it about fighting slavery.
And this is at a HS that Newsweek rates in the top 100. ARRRGH.

[Tom M King]

These are really good forums for woodworking.