Relative movement and agreement about an object's speed

[russ_watters]

In the picture, is B walking forward in the train at speed V? And you want to know the train and observer B's combined kinetic energy with respect to the ground? Then your reference frame of interest is the ground and you need to transform B's speed from train referenced to ground referenced.

It is a self contradiction to say that you want to use a reference frame on the train but want to know the kinetic energy with respect to the ground: "with respect to" means "that's my reference frame".

Also, you started talking about a plane in the picture. I assume you mean train. I don't want to be too critical, but that isn't just a typo, it is a potential sign of a disorganized thought process. I'm not sure you are putting enough serious effort into this: if you can't remember from one minute to the next if you are talking about a train or plane, how can you remember which reference frame is which?

 

[Quarlep]

n the picture, is B walking forward in the train at speed V?

Yeah B in the train at moves or walks at speed v

And you want to know the train and observer B's combined kinetic energy with respect to the ground?

I wanted to know kinetic energy of train resbect to RF.I mean there's.RF is a point in the train.RF means referance frame point and there's also observer in that point.

t is a self contradiction to say that you want to use a reference frame on the train but want to know the kinetic energy with respect to the ground: "with respect to" means "that's my reference frame".

Again referance frame is a point in the train which I showed in the picture.

Also, you started talking about a plane in the picture. I assume you mean train. I don't want to be too critical, but that isn't just a typo, it is a potential sign of a disorganized thought process. I'm not sure you are putting enough serious effort into this: if you can't remember from one minute to the next if you are talking about a train or plane, how can you remember which reference frame is which?

It sound like stupid or sllLy but I am in high school.And my first language is not english.And my father died few months ago so I can't focus on things.We didnt learned referance frames and relative kinetic energy at school I am tring to learn them here to ask questions and get answers. I am talking about train in the picture.Plane is just a example.

 

[russ_watters]

Yeah B in the train at moves or walks at speed v

I wanted to know kinetic energy of train resbect to RF.I mean there's.RF is a point in the train.RF means referance frame point and there's also observer in that point.

Again referance frame is a point in the train which I showed in the picture.

So, I think you know by now that the kinetic energy of the train with respect to point RF is 0.

OK...so why are frame A and man B even in the picture? Is there more that you want to know that you didn't say? It certainly seems like it because in the drawing you said:

I am trying to do put RF and A in the same reference frame.

A is a person on the ground. To put him in frame RF, the train will need to stop and pick him up. But this has nothing to do with what you previously said you wanted to know.

It sound like stupid or sllLy but I am in high school.

Not silly, disorganized. It is as if you are having two totally different conversations with different people and are sending us pieces of a conversation meant for someone else.

Back in the OP, you said:

Can they agree on kinetic energy cause of the observer inside the train no proof of movement ?

If the person in the train cannot see the ground and has no instruments, he cannot measure his speed with respect to the ground. But if they have phones, they can call each other and the person on the ground can call the person on the train and tell him the train's speed in the ground frame.

 

[Quarlep]

I'll be more spesific now.We are B.B is a physicist and he wants to calculate train energy.He picks a referance frame (which its RF)then he makes calculation he gets zero.Then B things "I know that A is moving with velocity v' now maybe I am moving to.If that's true then I have to calculate train energy more.But for that I need to think RF and A referance frames are same.Their (RF and A) referance frames must be same for that.That means I (B/physicist) need to think that I am moving v' cause I am inside the train.Then how can I prove that I am moving v'.I can't prove that I am moving but I can't prove also I am not moving v'".So train kinetic energy depends referance frame.If B thinks train moves v' same thing happens to RF and we will going to add extra energy.But again B can't prove both situations (I am moving or not moving) Is B can thing I am moving v' ?? Is that violates physics rules ??

 

[russ_watters]

There are no violations in there that I can see:
1. The train's velocity and kinetic energy with respect to RF are zero.
2. The train's velocity and kinetic energy with respect to A are not zero.
3. #1 and #2 do not contradict each other: velocity and kinetic energy are both frame dependent.
4. Whether the person on the train knows the velocity of the train with respect to A or not does not affect what the velocity of the train and kinetic energy with respect to A actually are. It just determines whether he knows enough to do the calculation.

 

[Quarlep]

There are no violations in there that I can see

"In There" means what I wrote or what you wrote

 

[russ_watters]

"In There" means what I wrote or what you wrote

In what you wrote.

 

[Quarlep]

Thank you

 

[Dale]

So train kinetic energy depends referance frame.

Yes. This is the key point. Anyone can choose to use any inertial reference frame they wish (no requirement to use their own), but that choice affects the value of the KE.