# Stefan

### Why does this happen?

When near an ocean during nighttime, with a clear visible moon, looking down at the water leads you to see a strip of reflected light, which abruptly ends. I am sure plenty of you are familiar with this scene. This "strip" moves along with you, that is, whenever you move the strip realigns itself to be underneath the moon and facing towards you. Kind of like this:

http://ih.constantcontact.com/fs012/1101454195791/...

Why is it only a strip and not the entire visible water?

2 AnswersPhysics5 years ago### How is it possible that someone can get electrocuted?

Consider that there is an uninsulated wire and I, while wearing shoes, touch the wire.

Do I get shocked? Yes, no, why?

If I am not wearing shoes but am standing on an insulated surface, do i get shocked? Why or why not?

1 AnswerPhysics6 years ago### In newtonian mechanics, why is the answer so?

Imagine there are two square masses A and B touching each other from one side mutually.

Mass A is of 1kg and Mass B is of 2kg.

A force is exerted on Mass A perpendicular to its surface and of magnitude 6N.

Calculate the overall acceleration of the system.

I found it to be 2, and agree with the answer.

Calculate the force A exerts on B and thus vice versa.

As shown in the image, the worked answer considers mass of B multiplied by the common acceleration.

This is of 4N.

But if I were to pick mass A... that would be 1×2=2N.

But by Newton's third law they should be both equal. So what is wrong please?

I really appreciate the help.

1 AnswerPhysics6 years ago### Help with differentials?

How would you find the general solution of

(1-x^2) y' - xy = 1

I tried by using the reverse of differentiation by parts but I got nowhere.

1 AnswerMathematics6 years ago### Find the number of shots required for the probability to hit the target becomes 0.9, if the chance of hitting the target is 0.4 per shot.?

What I tried to do is this:

I formed a series which describes the probability the gun will hit the target after each shot:

0.4 +0.6*0.4 +0.6*0.6*0.4 etc etc

But I do not know what method I can use to determine the LEAST number of terms which will add up to 0.9 or more.

3 AnswersMathematics6 years ago### If the Christian god has no creator why does he exist, what is his purpose?

Why would a god exist for the sole purpose to create everything for no higher purpose?

What is the point in watching a sandbox which has no value at all as you can do with it as you please?

There is nothing new going on, because this god would know it all along!

Would he laugh at Joe's joke?

He knew it before Joe was born!

What is the point? A deity's point?

10 AnswersReligion & Spirituality6 years ago### Find the nth roots of the equation?

(z+1)^n = 3 (z+2)^n

I appreciate all help! Thanks in advance.

1 AnswerMathematics6 years ago### Is there a Better way to solve this complex inequality problem?

I have been asked to find the greatest and least values of |z+1| from the following equation

|z+1+2i|=2

The book I use suggests a method of drawing a circle and finding the highest value from the origin and the lowest value.

I hate when mathematics falls in diagrams.

Surely there is an algebraic way to do this?

The answers are 2sqrt2 +-2

I tried the triangle inequality but the answers came out different.

2 AnswersMathematics6 years ago### How many integers below 10^46 have all their digits the same?

I've found this math site where the questions are just destructive.

2 AnswersMathematics6 years ago### Pulley system?

If I have two masses A = 2kg and B=4kg,

in a system that I am going to describe, what is the resultant tension in the string?

Basically, you have a smooth horizontal table, A rests on the table and is attached to a string which is attached to B.

B is hanging freely from one side of the table such that when time is resumed, B will fall and drag A with it.

How is the resultant tension 40/3 N please?

Thank you in advance!

1 AnswerHomework Help6 years ago### Sudden confusion about forces?

When we say W= F*d, is F a force acting throughout the whole distance travelled, or an initial force which causes the whole distance travelled?

Also, when a closed system containing only body A is subjected to some force F to the right, where does the reaction force emerge in the situation, due to Newton's Third Law?

1 AnswerPhysics6 years ago### Question about rotations about axis?

How does one determine which way, clockwise or anticlockwise, is the rotation positive?

For example if I have a rotation of 50 degrees in the xy plane, that is 50 degrees anticlockwise starting from the x axis.

If I had a 3d space, how would I figure out which direction, for example, in the zx plane, is the positive rotation?

2 AnswersMathematics6 years ago### Very recent tight pain in the very upper (opposite side to where the heart is) right chest?

Recently, like, 2 or one and a half days ago, I started feeling this uncomfortable pain which I can describe as tightening and brief. I consider it as brief not because it goes away in like seconds, but usually two minutes, and then it stops completely.

I seem to have actually found what is associated with it, and would like some guidance, preferably not from a troll, thank you.

Basically, every time I consume something which is particularly sweet, moments later, I feel this pain in the opposite side of the heart, and sometimes it is accompanied by a mild burning sensation in the stomach.

This pain and burning sensation ONLY occurs when I eat, not drink.

Could someone please guide me? I'd appreciate it, thank you.

1 AnswerPain & Pain Management6 years ago### Way with words?

If I were to say that

x is a positive integer and is not divisible by the square of any prime, what exactly am I saying?

Thanks.

3 AnswersMathematics6 years ago### Curious about a functions question?

If I have a function f(x) = sqrt(400-x^2)

and I strictly require it to be valid for real numbers, how many integers can I obtain for values of x?

You don't have to work this out, I am just curious about the method, because I cannot really think of a way to do this.

5 AnswersMathematics6 years ago### Can a general derivative of df(x) / dg(x) be computed, or is the denominator always strictly a sole variable?

For example, dx/d(x+5)

Can this be solved?

2 AnswersMathematics6 years ago### Forces and their directions?

I am finding a bit of confusion when it comes to equating forces.

For example :

When we consider satellites in a constant stationary orbit, we simply equate Newton's law of gravitation and the centripetal force equation, like so:

mwwr = Gmm/(RR)

Here, the centripetal force, acting downwards, is equal to the gravitational force, also acting downwards.

And I get that, they both have the same direction, so if the satellite stays in circular orbit, the forces must always be equal.

For my next example, when we equate Bqv with Eq in a velocity selector, we say that Bqv = Eq if the particle with charge q goes on in a straight line. (Due to a present crossed field)

The problem arises here.

If in gravitation, the gravitational force and the centripetal force act downwards both, I have no problem saying that they are equal.

However, in a crossed field, the electrostatic force is acting in the OPPOSITE direction of the magnetic force, so why is Bqv = Eq and not Bqv = -Eq?

Thanks I really need to have an answer for this, as I cannot understand this at all.

2 AnswersPhysics6 years ago### Matrix "hence" question?

Basically I have this matrix question.

I succeeded in the first part, and the answers match.

Here are the answers:

x= (1/22)(a-3b+11c),

y=(1/22)(5a+7b-11c)

z=(1/22)(-13a-5b+11c)

Now the problem really arises from the Hence part.

It also says "otherwise", so I simply found the inverse using the Adjoint method.

However I am curious, what did I miss?

How can I use the results of x y and z to find the inverse?

I do realize that the equations can form the given matrix.

Thanks in advance!!

1 AnswerMathematics6 years ago### Integral of arsinhx using logarithmic form?

I have came across a question which has already took a lot of my time, basically it states that I must use the relationship that arsinhx = ln (x+sqrt (x×x+1))

to integrate arsinhx.

I already know how to integrate arsinhx, but I couldn't really manage to integrate it in logarithmic form.

I tried using by parts and substitutions, but it quickly got messy and very tedious, is there a clean way to achieve this?

Thanks in advance!

3 AnswersMathematics6 years ago