Inertial reference question (1 Viewer)

[BrotherBread]

Fairly basic question I know but the experiment we did for this was a bit unorthodox and didn't explain it to me. So could someone help me out here.

You are flying on aplane at a constant velocity and drop a coin out of it, describe the motion of the coin as you observe it from the plain.

Explain how the observation made, illustrates that the plane was in an inertial frame of reference.

 

[Zero Infinite]

You are flying on aplane at a constant velocity and drop a coin out of it, describe the motion of the coin as you observe it from the plain.

The coin is going to have the same horizontal velocity as the plane, so from your POV it will travel straight down, as you in the plane will remain directly above it. A person from a distance will see the coin travel in a parabola.

Explain how the observation made, illustrates that the plane was in an inertial frame of reference.

An inertial frame of reference is one where you are travelling at a uniform velocity, or are at rest, and from the principle of relativity, there is no way to detect which state of motion you are in without reference to an outside frame. In this case, as the coin travels straight down from your POV you can't tell what state of motion you are in. Only from an outside observer's POV where they saw the parabolic trajectory of the coin can it be said that the plane is moving.

Hope this is what you were looking for.

 

[BrotherBread]

Yeah it was thanks very much Zero.

chousta, I guess it is saying explain how the observations made show that the plane is in an inertial frame of reference with the coin.

 

[jyu]

You are flying on aplane at a constant velocity and drop a coin out of it, describe the motion of the coin as you observe it from the plain.

The coin is going to have the same horizontal velocity as the plane, so from your POV it will travel straight down, as you in the plane will remain directly above it. A person from a distance will see the coin travel in a parabola.

Explain how the observation made, illustrates that the plane was in an inertial frame of reference.

An inertial frame of reference is one where you are travelling at a uniform velocity, or are at rest, and from the principle of relativity, there is no way to detect which state of motion you are in without reference to an outside frame.

In this case, as the coin travels straight down from your POV you can't tell what state of motion you are in. Only from an outside observer's POV where they saw the parabolic trajectory of the coin can it be said that the plane is moving.

Hope this is what you were looking for.

In this case, as the coin travels straight down from your POV you can't tell what state of motion you are in. Only from an outside observer's POV where they saw the parabolic trajectory of the coin can it be said that the plane is moving.

The above atatement did not explain why the plane was in an inertial frame of reference. You cannot tell what state of motion you are in, but you can tell whether you are in an inertial frame of reference or not. If you are in an inertial frame of reference, Newton's laws of motion are true. You are flying in the plane observing the motion of the coin, which follows
a = F/m = mg/m = g.

:wave:

 

[dr baby beanie]

wait, doesn't the coin travel, say to the 'right' if the plane is travelling to the 'right' because of the horizontal motion, as viewed from an outside observer, who will see the coin fall, in like a half parabola shape, to the 'right'?

 

[idling fire]

From inside the plane, I would have said that you can't even see if the coin falls at all really, other than perspective...

You'd be looking straight down on it and it wouldn't look like it's moving, so you cannot detect your own motion either, without external reference points.

 

[jyu]

From inside the plane, I would have said that you can't even see if the coin falls at all really, other than perspective...

You'd be looking straight down on it and it wouldn't look like it's moving, so you cannot detect your own motion either, without external reference points.

Not true. There are many ways to detect the motion of the coin from the plane, e.g. you can see the coin becoming smaller as it moves away from you.

:wave:

 

[idling fire]

Not true. There are many ways to detect the motion of the coin from the plane, e.g. you can see the coin becoming smaller as it moves away from you.

:wave:

Righto. I did say,

other than perspective...

Yeah I see what you mean now though. Laser detector and data logger etc.
I plea half asleepness.

But you still technically wouldn't SEE it moving in a straight line.

 

[Snarkie]

I had a similar question in my textbook and this is how they explained it (to put it into the context of this question, my book used a car): You can tell that it is an inertial frame of reference as all the laws of physics applies the same, the same law of gravity and same laws of motion and acceleration is the same. In the frame of reference of an observer outside the plane, the coin will have an initial velocity equal to the plane's. The laws of physics therefore predict it will follow a parabolic path like any projectile. In the plane's reference frame, there is no initial velocity (as it is travelling at constant speed and therefore the observer feels no motion) and the laws of physics therefore predicts that the coin will fall straight down. They have the same laws of physics in both reference frames (hence, they are inertial frames of reference) but they specify different pahts.

It's pretty much word by word from my textbook, but I hope it was helpful.

 

[Forbidden.]

Fairly basic question I know but the experiment we did for this was a bit unorthodox and didn't explain it to me. So could someone help me out here.

You are flying on aplane at a constant velocity and drop a coin out of it, describe the motion of the coin as you observe it from the plain.

Explain how the observation made, illustrates that the plane was in an inertial frame of reference.

How I would answer it:

The coin drops out of the plain in a straight line (because unless other factors are mentioned, I assume the plane travels straight).

The plane was an inertial frame of reference because the plane is moving at a constant velocity.

Both the plane and coin is subject to the same initial horizontal initial velocity and since vertical velocity of the coin only is affected by gravity and horizontal velocity is always constant neglecting wind resistance, then both the plane and coin would move at the same horizontal velocity as each other, even as the coin falls.

An observer from below watching the plane's side would see the coin drop in an arc.