What conditions define a spacetime path? The answer is supposed to differentiate ageing from reciprocal time dilation and permanent age difference due to a change in relative velocity as in the twin paradox. I won't be communicating with anyone posting links to wiki articles. If you see no difference between reciprocal time dilation and age difference, please don't try to respond.

Sample answers are:

1. True permanent age difference can only be established if the two participants start together, one makes a change in relative velocity and they both re-unite. Hence, relativity forbids making any determination of permanent age difference if the change in relative velocity is a slow down (not quite a stop) or a speed up.

2. An exception is when the change ends in a relative stop, they remain separated but the end of the spacetime path is when the news, via light signal, of the change reaches the other party. It's somehow not as valid as point 1 because their separation allows another frame's line of simultaneity to calculate a different permanent age difference from the one they see between them or the space between them has a time value that does not appear on clocks and can only be exhausted by re-unification. I never got a clear answer on this.

3. Unchanged constant relative velocity does not result in age difference. Some contend age difference is a matter of perspective and so constant relative velocity does result in age difference, equal from each perspective. Others say age difference can't be established because there is no valid end to the spacetime path. Others say because time dilation is reciprocal, the two perspectives cancel out and that's why there's no age difference.

4. At what point in the spacetime path does the age difference occur? Relativity's answer is that age difference can only be determined at the end of the spacetime path. Any attempt to look at how it progresses during the path is forbidden. Others say there is a jump in age difference during the swing in the initiator's line of simultaneity. Other's say there are two jumps, one at the velocity change and another at the end. Most say age difference progresses incrementally and identically to reciprocal time dilation in a spacetime path. They say there is no difference between the two even though the twin paradox proves there is.

5. If relativity does not forbid looking at how age difference unfolds, then why are there two different answers depending on which party is depicted as stationary? ]]>

I initially thought that as it approaches trans sonic speed, shockwaves start to form inside the lattice (choked flow), which starts to create a little more drag. As it nears M1, a bow shock will form which would start diverting air away from the lattice and at the same time would create significant drag. A normal shock wave and oblique shockwave should form at this time, further increasing drag as speed increases and the bow shock eventually disappears. Yet as the fins start to go past M1, the oblique angle increases which would be associated with lower temp/pressure drops which would explain why the Cd decreases ? Wouldn't this contradict the Mach vs Force graph where the drag force keeps increasing?

This feels wrong but I did the best I could. I'd love to hear the flaws in this attempt. ]]>

block 1 follows block 2 on a frictionless surface. Block 2 has a spring attached behind it with

Block2-> m2=10.0kg v2=6m/s

The collision between the two is totally inelastic. And after the collision block1 and block2 move with

I tried finding the kinetic energy from block1 and then the kinetic energy after the collision. I thought the sum would give the amount of potential energy stored in the spring. And finding the distance with Epot=0.5*kx^2

The way I find the kinetic energy from block one is taking the relative velocity between the blocks-> 20m/s-6m/s=14m/s.

Then Ekin=0.54kg14^2

And Ekin2=0.5(m1+m2)(10m/s)^2

then Ekin2-Ekin=-308J

Solving for x with Epot=308J gives me a distance of 0.75m

The answer is supposedly 0.71m ]]>

I need help with a task, it goes like this:

So, here is the problem:

I need to create a water system for cabins. the water system consists of a tank (see picture) with different outlets for pipes and one or two pumps that will provide the supply of water to the cabins. the tank is 20 m lower than the cabins. The water should be pumped upwards. The estimated water consumption is 350-500 l / per day.

Make a simple drawing of the water plant with the cabin field. Find a suitable pump that you would recommend for the transport of the water to the cabins. depending on the distance from the tank to the cabins and the number of cabins, it may be necessary to use 4 pumps as there are 4 cabins. maximum distance from the water plant is recommended and should be found. attach documentation to the selected pump and indicate which assumptions and choice of pump is based, that is why you have chosen that pump.

The pumps are selected from a website that I have the link for. And to find the right pump, I have to use bernoullis equation and use pump performance curve (I have a model in Excel for that) ]]>

I have bought a pair of Eschenbach loupe glasses: https://www.cambridgeoptics.com/WebR...Specticals.jpg

I didn't know that they come in 'near' or 'far' versions.

I bought the 'Far' type, but need the near type for electronics.

I think these van be modified by adding an optic to the front of the glasses, and need to find suitable ones.

I have a standard Loupe, which is x10 I took it apart and there are two optics inside. One of thes optics placed on the front of the glasses, brings the focus to app 70mm. I need to focus app 400mm.

Can anyone explain where I can buy suitable optics please?

Camerart ]]>

Is it a large band gap or short band gap material? ]]>

"when mechanical work is done on a system of gas, the internal energy of the system increases."

According to the formula of the First Law of Thermodynamics,it sounds true.

But ,theoretically, when we do work on a gas , it compresses,i.e.,its volume decreases.When volume decreases than temperature should also decrease as 'v' is directly proportional to 't'. In case temperature decreases, than internal energy will also decrease.

This is a clear-cut contradiction of the above statement.

I feel i am wrong somewhere because the statement can't be wrong.

Plz somebody help me point out my mistake.

Thanks in advance! ]]>

For b) I was curious why i couldn't use s = ut + 0.5at^2 as my equation as i had all the necessary known values.. instead to get the correct answer i had to use v=u + at

why is this so. Thank you for your time

Picture of Problem: https://imgur.com/a/GruxPwe ]]>

I am trying to figure out why the answer is T>W... do you have any idea why, if so could you please explain. Thank you.

Picture of Problem: https://imgur.com/a/Mp2eAjc ]]>

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