Question

PLEASE HELP ):

Explain what it means to view a moving object from a frame of reference. Provide an example that illustrates your explanation.

Answer 1

it means nothing but viewing a same thing in different angles in different positions in different situations.....

you can ask if you want example...???

Answer 2

In the most precise version of "frame of reference," all the information is laid out with something defined as a reference.

Usually, people look at velocity, and I'm wondering if that's what you're doing in class now!

So, suppose you're walking to class. You might think you're walking at 3 miles/hour. Now, you are walking 3 miles/hour relative to \(what\)? The reference frame defines this. If you did that, you would be thinking about yourself in a reference frame where the ground "moves at" 0 miles/hour. Right?

Now, what if you said that your velocity was 0? You can do that. If you're walking to class, the world would be moving 3 miles/hour away from class.

Try this! Walk. And then imagine you are standing still and everything else is moving. If you can feel that, then you just thought about a \(different\) reference frame!

Got it?

The same is true for time. I can say that right now is the \(t=0\). By the time you finish this sentence, which I guess takes 2 seconds, we're at \(t=2\).
I could look at this from a different reference [frame] though. Say I figured it would be cool to say that when I said \(t=0\), I say \(t_2=1\). Then, when you finished the sentence, it was more like \(t_2=3\), 2 seconds passed. You might not think of this as a different reference.... But the reference for \(t_2\) is at a different place in time, and everything is compared to that reference when we talk about \(t_2\).

[[For a brain teaser, assuming you have any free time, find the zero reference for \(t_2\), as seen from the reference frame involving \(t\)! Answer at bottom.]]

I picked out velocity and time, but they are different attributes that each have references. A reference FRAME has references for each attribute that you care to mention.

What are they good for?
1. Seeing things from a different point of view.
2. Comparing things.
I have a two toy cars colliding. One red car heading 5mp right, the other is a blue car heading 3mph left. (That's where ground's speed is zero.) How fast are the cars coming at each other? Well, magically jump into the 5mph red car, and look only at the blue car, it looks like it's coming at 8mph (because you just considered a different reference frame, where the red car is still and the blue car is coming at it).

I hope this helps! Feel free to ask questions. If I'm around, I'll take a look!



[[Answer to the brain teaser from before: if \(t_2=0\), then \(t=-1\). So, it depends what your reference is, one or the other.]]

Answer 3

Bravo @theEric Bravo.... I didn't read that... still Hats off to your patience on it....keep it up
lol...

Answer 4

Haha, thanks @harishk ! :D

Sometimes I have this problem of writing too much :) But I really hope it helps! Thank you!

Answer 5

@theEric
Good example of different space-related frames of reference.
You can also describe the motion of a dropped object when you are sitting on a train. In the train's frame, the path is linear, whereas in the ground's frame, the path is parabolic.

On the other hand, what you are describing with the clocks is just a change in time origin, not a change in the time-related frame of reference: any two simultaneous events for the first clock will be simultaneous for the second one. Any duration measured with the first clock will give the same reading as with the second clock. This is no wonder since in newtonian mechanics there is an absolute time, i.e. there is a unique time reference-frame.

So, in order to distinguish motion seen from two different frames, changing the space reference frame is the only option, at least in classical mechanics.

Answer 6

I remember the picture when I was young and took my very first physics lessons, of me standing on Earth and looking at two things: The Moon and tree. Obviously the Moon was moving and tree wasn't. So in one frame of reference I can see things that can move and stand still. But if I were on Moon I could see the Earth and tree moving. Also when I drive my car from my frame of reference every thing in the car including the car doesn't move. But from the other frame of reference e.g. person standing on the ground the car and me move. From the practical point of view we can really simplify our calculations while considering motion( look the car example given by theEric). another example: two objects are moving with constant velocities v1 and v2 in different directions. How far apart will they be after t seconds? In this case you can really simplify your life by choosing different frame of reference from ground, i.e. relative to one of these objects:
so if you are able to find that velocity v2-v1 the distance after t seconds would be (v2-v1)t

Answer 7

I like your responses, @Vincent-Lyon.Fr and @Fifciol ! :) :)

@Vincent-Lyon.Fr , would the time thing I had an example of still count as frame of reference? I know it wouldn't be a different inertial reference frame. But I was looking at Wikipedia, and it makes sense to me. I would say the same thing about distance, too, the way I see it. I see it, in general, as defining a view of the world in which all things are relative.

"In physics, a frame of reference (or reference frame) may refer to a coordinate system used to represent and measure properties of objects, such as their position and orientation, at different moments of time."
- http://en.wikipedia.org/wiki/Frame_of_reference

And so (because of the Wikipedia article) I was thinking that the time example of mine was when a specific coordinate system was involved. Is that a common view? Or does that not count as part of a reference frame
I think it's still important.. Like, three people waiting in a line. Both have the same axes - I mean they're parallel. But they each define themselves to be at the origin position. Then the sign can be used for towards the front of the line (+) or towards the back of the line (-). Out of the three people, the sign depends on whose reference frame you're considering. Does anyone see reference frames like that, or did I make a mistake?

Thanks!

Answer 8

I'll try to make a longer answer later, but I'm afraid the Wikipedia article is one of the worst among those concerning physics and should not be taken as a starting point.

It is flawed with many contradictions and errors in different paragraphs.
The main reason is that is starts by saying a frame of reference IS a coordinate system, whereas the right thing to say would be:
- any coordinate system can define a unique frame of reference
- any frame of reference can be associated to an infinite number of interdependent coordinate systems, fixed relative to one another.

In shorter words:
- a frame of reference is a physical concept
- a coordinate system is a mathematical concept

For space, an easier definition of a frame of reference is "a solid or a set of fixed points relative to each other"
- earth
- train
- car
- merry-go-round
- satellite cabin

Then, and only then, can the definition be extrapolated to the useful geocentric or heliocentric frames.

Answer 9

Thank you very much, @Vincent-Lyon.Fr!