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YO all!

After spending some time with physics,I came up with thoughts:
These might/might not be true,put your thoughts,all welcomed

*Acceleration is the essence of velocity

*Hot tubes are also dangerous when they are dry,the high voltage thing in your hand might kill you even if you are just laying in a perfectly dry hot tube,provide that your feet is touching the metal piece that is linked to the sink
And water is just an element for the kill to happen

I am not a very good student,to be honest,so I might be crazy talking here

Forgive me for my foolishness

What are hot tubes?

I didn't understand any of that.

hot tub?

I really don't see how acceleration is the "essence of velocity". It only becomes relevant when velocity changes. If anything the "essence" of velocity is direction, as it's a vector quantity.

+1 on Dreads post.


Speed is Distance over time. Example 6M/Sec
Velocity is the Speed plus direction. Example 6M/Sec north,
Acceleration is the change in velocity or Δv


As for the rest of your post it is gibberish.

The best help I can offer is the idea that pure water does not conduct electricity so to be safe you should fill your Hot Tube with R/O Water.

You don't need an acceleration to have a velocity.

Water is not an element, it is a molecule. Clthomps is correct in saying that pure water is not a good conductor as it lacks ions, however i don't suggest you test this theory with your bath as the water coming out of the tap will likely be quite impure, containing many ionic compounds.

Here's a better question:

A small spacecraft is falling into a gravity well with a velocity roughly equal to 100Kps. A beam of light is shone from one end of the spacecraft to the other. Describe how this beam of light would appear to a) an observer inside the spacecraft b)an observer position independently of the spacecraft.

J.Black wrote:

A small spacecraft is falling into a gravity well with a velocity roughly equal to 100Kps. A beam of light is shone from one end of the spacecraft to the other. Describe how this beam of light would appear to a) an observer inside the spacecraft b)an observer position independently of the spacecraft.

100Kps, did you mean kms-1 or Kpcs-1(kilo parsecs per second)as the latter speed is significantly greater than c ( the speed of light in a vacuum),this question makes little sense either, to me anyway.
i guess you were asking about redshift?

By Kps, i mean kilometres per second. Was trying to keep the nomenclature simple and not involve measurements like parsecs (which would have required a paragraph or so of explanation and a diagram). Just showing that the spacecraft is travelling at a significant fraction of the speed of light.

Think 'frames of reference'

ok, so a) to an observer on the craft the light will appear as it is emmitted, unchanged.
b) the light would appear at a lower wavelength due to redshift, z.( like the doppler effect but light wavesinstead of sound waves)
in fact, i believe that the craft would continue to gain speed to to the force of accelleration due to gravity(the magnitude of this force is proportional to the mass of the nucleus of the 'gravity well' and the mass of the craft), so to an independant observer ,over time the light would infact continue to decrease in wave lenght, towards the red end of the spectrum as the craft accellerates further.
But I could be wrong! @JB. is that the answer you were looking for, or am I way off?

If there is no acceleration there is no velocity right?
I am speaking in a real life thing here
If there is no change in speed,there is no speed,because everything starts at zero right?

Tony the guardsman wrote:If there is no acceleration there is no velocity right?
I am speaking in a real life thing here
If there is no change in speed,there is no speed,because everything starts at zero right?

Well yes you need to accelerate at least once to move... this is pretty obvious and is common sense not physics.

Tony the guardsman wrote:If there is no acceleration there is no velocity right?
I am speaking in a real life thing here
If there is no change in speed,there is no speed,because everything starts at zero right?

Unless you are already moving... There is no requirement that you be stopped. In fact even if you are sitting very very still right now, you are moving rather quickly around the sun.

If you are moving, then to slow down or speed up you will need to accelerate (or decelerate) .

According to newton, an object is at rest when it is moving at a constant velocity. it is only with the addition of an unbalanced force that the object direction or speed changes( accelleration).
so energy IS........force may or may not be.

Tony the guardsman wrote:"Unless you are already moving... There is no requirement that you be stopped. In fact even if you are sitting very very still right now, you are moving rather quickly around the sun.

We are both on earth right now,so there is no point talking about moving around the sun;there is no absolute movement,it always depends on the point of view you are watching from

Tony the guardsman wrote:
It depends on the point of view you are looking at this,we are both on earth so no need to talk about moving around the sun

I happen to be posting from an Airplane moving East from CA to MD at 450 MpH.
You are reading this in a car driving on the freeway north at 55 MpH.
If I want to throw you a ball, I need to figure out where you will be when the ball gets there.
If I want you to catch the ball, I should try to figure out how to slow it down enough that it won't adversely affect your hand when you try and catch it.

I think someone's posting while high.

Tony the guardsman wrote:
*Hot tubes are also dangerous when they are dry,the high voltage thing in your hand might kill you

said the actress to the bishop

Gah. What a horrible mess :S

The answer is as follows:

a) The light will appear to move in a straight line from one side of the spacecraft to the other.

b) The light will appear to curve down as it travels across the craft.

This was intended as a simple proof of the notion the that light does not travel in straight lines. The particle-wave duality exhibited by photons makes them susceptible to gravitic forces and produces a relatively well known effect called Gravitational lensing A fact i suspect is not taught in most high schools.

@Uri Lee: What you've said is pretty much correct. Redshift depends upon the distance of the observer from the light source and the relative velocities involved. If the observer was close enough to see the beam of light, it can be assumed that they were not far away enough for any redshift to be apparent.

@Tony:

We are both on earth right now,so there is no point talking about moving around the sun;there is no absolute movement,it always depends on the point of view you are watching from

This pretty much answers my original question. From the point of view of someone on Earth, they are stationary and it is the Sun that is moving, and vice-versa. A lot of General relativity depends upon the position (frame of reference) of the person/device that is viewing the event.

However, just because you are on the Earth does not mean that you are in the same frame of reference as someone else. If you or the other person have a velocity/acceleration you need to take something called the Lorentz contraction into account. This basically states that a moving observer must modify all distances/times that they record with respect to the event they are observing

See, isn't Physics fun!

J.Black wrote:

This was intended as a simple proof of the notion the that light does not travel in straight lines. The particle-wave duality exhibited by photons makes them susceptible to gravitic forces and produces a relatively well known effect called Gravitational lensing A fact i suspect is not taught in most high schools.

I was under the impression that gravitational lensing was caused by the curvature of space itself due to the gravitational field, therefore the light IS still travelling in a straight line, through CURVED space. Well at least according to Einsteins theory of gravity, but still, he could also be wrong, as could I.

Technically correct sir

Describing the curvature of space does lead to some pretty complex mathematics though :( I thought it would be better illustrated using frames of reference as they only require three dimensions

Hopefully the LHC can shed some more light on Einsteins theory as it does break down at a few points, not least of them being why he had to stick an arbitrary constant into his equations to make them work.

As to why a hot-tub can kill you, I think you may be confusing voltage with velocity (which has already been addressed) in your original
reasoning, Tony the gaurdsman. Voltage measures the difference in electrical energy between two points (if I'm remembering my
electronics course correctly). Reason electricity is dangerous is that we use it in our bodies to control everything in the body, esp. the
the heart. You get hit with the right voltage across your chest, and you'll be taking a trip to the emergency room. The same principle
applies when you get hit elsewhere. I was changing out some light-switches at my parents house a couple of years back, and the circuit
was supposed to be off. Stuck my leatherman in there an took a nice 120v shock. Threw the tool to the other side of the house because
the electricity from the wall over-powered the signals from my brain to my arm and resulted in the muscles doing their own thing. Lesson
learned: don't trust the labelling on the breaker when the house was built in the 50's and the people who owned it the 20 years prior to
your folks moving in are red necks of the second highest order (there weren't cars on blocks when they bought it, but you wouldn't beleive
the work they had to put in on the inside). Incidentally, if it had been d/c instead of a/c my arm would have clamped down, and
I'd probably be dead. D/C goes in one direction only, so your muscles lock, while a/c changes direction fast enough to cause your muscles
to spasm.