Space question (1 Viewer)

[velox]

calculate the mass of a 85kg person on the moon. (acceleration due to gravity is 1.6ms on the moon)

Isnt the mass always the same? Or have i read the question wrong?

 

[nomz]

yeah its a trick question. Mass is always the same. Its the weight that changes.

 

[Tommy_Lamp]

its a trick question
the answer is 85kg

i think the 2002 HSC they question askign you to measure the speed of light in a certain situation and the answer was 3x10^8 because its constant

 

[jumb]

Half yearly had one on 'height' dilation.

 

[gordo]

the speed of light isn't constant

the speed u get on a data sheet is the speed of light travelling through a vacuum

they can slow light down by shining it through materials with different refractive indexes.

 

[velox]

thanks.. Yeah Gordo ur right also

 

[gordo]

oh
u meant like relativty
2 different observers in differeing frames of referrence will see the same light wave travelling at the same speed (but that speed is not necessarily 3x10^8)

 

[BillyMak]

What if the two frames of reference are separated by a big sheet of glass, and one frame of reference had air while the other was a vacuum?

 

[xiao1985]

air and vacuum have significantly similar refractive index if my mem serves me right... so u can assume they speed of light is constant...

in any case, just be mindful of the speed of light varies... idon't think tis assessble in hsc...

 

[adinclik]

C

Gordo,check this out about the speed of light's constancy. The speed of light does travel at a constant speed, however, since light is actually a bunch of photons, when entering a new material, thay get absorbed by atoms, and released again. The speed of light is constant between the atoms (since it is a vaccuum), yet when the photons are absorbed by atoms, they tend to seem as if light is slowing down at the macroscopic level. It is actually the absorption-releasing process of the atoms that makes light seem to slow down in a substance. this is why the denser the material, the slower light seems to travel (i.e. more atoms absorbing and releasing photons, causing a lagging effect).

I hope this answers what you have written before.

 

[Xayma]

Yes the speed of light is a constant, the velocity however, is dependant on the material. But they won't use velocity often because it can be affected by gravity, ie gravitational lensing.

 

[adinclik]

Yes the speed of light is a constant, the velocity however, is dependant on the material. But they won't use velocity often because it can be affected by gravity, ie gravitational lensing.

The velocity of light still has to be constant in any material, due to the fact that between individual atoms is a vaccuum, in which the speed of light travels at C (constant speed of light in a vaccuum). The reason y it seems to slow down id, as i already stated, the absorption and releasing of photons by atoms in a substance. Every absorption and releasing of a photon takes a tiny amount of time, so trillions and zillions of atoms absorbing and releasing photons would make it look like light is slowing down, from our view.

What you're saying is that the speed of light slows down in a denser substance. This is what i also said when i saw the light from a lighthouse on a foggy day. it seemed as if the light was travelling slow enogh for me to watch its movements with my naked eye. But there is a vaccuum between every atom, which means that the speed of light in this vacuum (in any substance) is constant. i guess you know what im trying to say...

 

[Xayma]

I suppose you could say the speed of light changes, but I wouldn't consider the time it is absorbed to when it is remitted to be considered. Anyway as far as the HSC goes in air it is negligible difference, about as much as the difference between 3*10⁸ms^-1 and the actual value.

 

[t-i-m-m-y]

what about; if we take the sun's as our interial frame of reference. the moon is moving around- mass dilation

 

[Tommy_Lamp]

what is the speed of light is actually 0, and we are all moving at 3x10^8

blah blah blah

BAH

 

[matt_f64]

xayma can u please remove that bloody picture (avatar) of urs... it is not necessary... ARGH

 

[matt_f64]

ie. ugly.....

 

[Xayma]

A few things, why the fuck did you bother to post?

I really don't care about you, if you are that annoyed at it, disable the showing of avatars.