Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: guest39538 on 22/02/2016 10:10:48
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Hello, I was asked a question by my 15 year old cousin and did not know what to answer.
He ask's
a Journey from A to B takes 1 second to travel at v=c
a journey from B to A takes 1 second to travel at v=c
distance (d) = X=?
net difference d/ t = ?
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net difference d/ t = ?
you must have misunderstood the question, d/t is not a difference it is a speed if d is the distance (easily calculated using the speed of light).
You need to go back and ask for clarification.
PS - Net (or Nett in US) means a part of something, like Net income is income after deductions such as tax.
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net difference d/ t = ?
you must have misunderstood the question, d/t is not a difference it is a speed if d is the distance (easily calculated using the speed of light).
You need to go back and ask for clarification.
PS - Net (or Nett in US) means a part of something, like Net income is income after deductions such as tax.
I have asked and he says, he was asking about the net difference between the two travelling bodies d/t
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I have asked and he says, he was asking about the net difference between the two travelling bodies d/t
there is no net difference the distance is the same, the speed is the same. If you want to consider these as vectors, you would define one as +ve and the other -ve, net difference 0.
Always happy to help with homework questions by giving hints, but in this case I still don't understand the question.
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I have asked and he says, he was asking about the net difference between the two travelling bodies d/t
there is no net difference the distance is the same, the speed is the same. If you want to consider these as vectors, you would define one as +ve and the other -ve, net difference 0.
Always happy to help with homework questions by giving hints, but in this case I still don't understand the question.
Well I also thought the net difference was 0. I think you answered the question, thanks Colin.
A question of my own, why would you define -ve and +ve , is this to show the invert velocity?
what does the e mean?
and how would you express net difference in a symbol form?
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A question of my own, why would you define -ve and +ve , is this to show the invert velocity?
No just direction.
what does the e mean?
+ve is just shorthand for positive.
and how would you express net difference in a symbol form?
Not aware of a symbol
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A question of my own, why would you define -ve and +ve , is this to show the invert velocity?
No just direction.
what does the e mean?
+ve is just shorthand for positive.
and how would you express net difference in a symbol form?
Not aware of a symbol
arrghh I see. So would I express for the above question
+ve=c
-ve=c
d=x
net difference t=0
Explaining a back and forth journey?
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d=x
net difference t=0
Explaining a back and forth journey?
No, how can t=0 if you went there and back?
If you went there and back then d=2x and time =2t
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d=x
net difference t=0
Explaining a back and forth journey?
No, how can t=0 if you went there and back?
If you went there and back then d=2x and time =2t
I think you may of misunderstood or I have not explained greatly.
We were individually accessing two trips, the first trip from A to B then the second return trip of B to A , and calculating the net difference in time of each trip at constant velocity of c in either direction.
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OK, this confused me:
"net difference d/ t = ?"
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OK, this confused me:
"net difference d/ t = ?"
Yes I probably should of put
net difference d/t^2 =0 or ∑(+ve⊥-ve)=Δv=(d/t^2)=0
To show both journeys was equal in every aspect. Would that be more understandable?
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The important thing about the question is the realisation (following the experimental discovery) that c is constant regardless of direction, so A-> B = B->A in every respect.
Obviously d = 300,000,000 km or thereabouts.
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The important thing about the question is the realisation (following the experimental discovery) that c is constant regardless of direction, so A-> B = B->A in every respect.
Obviously d = 300,000,000 km or thereabouts.
Yes indeed the importance is to realise that c is constant regardless of direction and a set length of x in either direction the photons would take the exact same amount of time to arrive at each others destination.
Would you say that at the exact half way point of X would be the exact position of passing photon's from each direction?
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how would you express net difference in a symbol form?
In mathematics, physics and chemistry, the Greek letter Delta ("d" sound) is often used to represent a difference:
- "Δ":Capital Delta
- "δ": lower case delta
Sometimes the equivalent English letter "d" is used to represent a infinitesimal difference (as in velocity=ds/dt).
...and a "curvy d" () in more complicated scenarios.
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how would you express net difference in a symbol form?
In mathematics, physics and chemistry, the Greek letter Delta ("d" sound) is often used to represent a difference:
- "Δ":Capital Delta
- "δ": lower case delta
Sometimes the equivalent English letter "d" is used to represent a infinitesimal difference (as in velocity=dt/dt).
...and a "curvy d" () in more complicated scenarios.
Then maybe simply dt/dt=0 net difference?
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Then maybe simply dt/dt=0 net difference?
no, dt/dt=1
for a difference you have to subtract eg t1-t2=δt
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Then maybe simply dt/dt=0 net difference?
no, dt/dt=1
for a difference you have to subtract eg t1-t2=δt
In my scenario
t1-t2=o
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Then maybe simply dt/dt=0 net difference?
no, dt/dt=1
for a difference you have to subtract eg t1-t2=δt
In my scenario
t1-t2=o
You can't simply subtract t2 from t1. Both of the time intervals are in the same direction since time does not go backwards. You gain nothing from the operation. It would be different if the time component was part of a velocity calculation. As that has a well defined direction since it is a vector.
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You can't simply subtract t2 from t1. Both of the time intervals are in the same direction since time does not go backwards. You gain nothing from the operation. It would be different if the time component was part of a velocity calculation. As that has a well defined direction since it is a vector.
I agree Jeff, I was thinking of an example such as 20s-5s=15s.
To subtract the 2 journey times is pointless.
My fault, I'd forgotten where this strange topic had started from!
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Then maybe simply dt/dt=0 net difference?
no, dt/dt=1
for a difference you have to subtract eg t1-t2=δt
In my scenario
t1-t2=o
You can't simply subtract t2 from t1. Both of the time intervals are in the same direction since time does not go backwards. You gain nothing from the operation. It would be different if the time component was part of a velocity calculation. As that has a well defined direction since it is a vector.
its a net difference calculation of two journeys I need. two directions, the same speed and distance.
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ok, just to be clear.
If you travel from home to nearby town and it takes 1hr then return journey is also 1hr. Total journey time (round trip) is 2hr, but the difference between the 2 journey times is 0, in other words they are the same.
Sorry to labour this but we've got to be clear to avoid misunderstandings
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If we take two vectors V1 and V2 this can be demonstrated. V1 starts at the origin [0, 0] and has an endpoint at [2, 2]. Vector V2 starts at [2, 2] and has its endpoint at the origin [0, 0]. To simplify the calculation we can translate V2 to The origin so that it starts at [0, 0] and its endpoint is at [-2, -2]. We can then simply add the vectors together using the endpoint values. [2, 2] and [-2, -2]. As can be seen the addition of 2 and -2 in both cases results ultimately in a null vector with both starting and ending points at [0, 0]. This indicates a velocity of zero for the round trip which could imply no time if you didn't have all the information about the past states of the system. Here information about the system is lost and so shows that information is generally not conserved with the flow of time.
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ok, just to be clear.
If you travel from home to nearby town and it takes 1hr then return journey is also 1hr. Total journey time (round trip) is 2hr, but the difference between the 2 journey times is 0, in other words they are the same.
Sorry to labour this but we've got to be clear to avoid misunderstandings
Yes exactly that.