I Saw This on Another Forum and I Don't Know How to Answer This Question

[Questioning Physics]

If a jet is flying 600 miles per hour in the same direction the earth is rotating, and the earth is rotating 1,000 miles per hour, how does that jet get to its destination when it is flying 400 miles per hour slower than the earth is rotating?

 

How do I answer this? What do I tell them?

[Strange]

What is the speed of the jet relative to?

 

If it is relative to the Earth, then it is moving at 1,600 mph and can quickly reach the destination.

 

If it is measured relative to the same thing that the Earth is, then it is flying backwards and will reach the destination by going the other way round the world.

Edited October 27, 2014 by Strange

[Questioning Physics]

If a plane is flying from New York to Los Angeles and another plane is flying from Los Angeles to New York and both planes left their airports at the same time and are traveling the same speed, since the earth is rotating 1,000 miles per hour in one direction, how is it that both planes reach their destinations at the same time?

[sunshaker]

I see it the same as two passengers on a train walking from opposite ends of train, will meet in the middle how ever fast or in what direction the train is going.

[Strange]

If a plane is flying from New York to Los Angeles and another plane is flying from Los Angeles to New York and both planes left their airports at the same time and are traveling the same speed, since the earth is rotating 1,000 miles per hour in one direction, how is it that both planes reach their destinations at the same time?

 

Because they are moving at the same speed relative to the Earth. Imagine the Earth stationary and the problem goes away.

 

All motion is relative. You are mixing "frames of reference".

 

In one (the Earth's) the two planes both flay at, say, 600mph and the earth doesn't move between them.

 

In another frame of reference, the Earth is moving at 1,000 mph, one plane is moving at 1,600 mph and the other is moving at 400 mph.

I see it the same as two passengers on a train walking from opposite ends of train, will meet in the middle how ever fast or in what direction the train is going.

yes, that's a good example.

[Questioning Physics]

How do the planes meet in the middle when the earth is moving 1,000 miles per hour away from the one plane? The speed of the earth will not allow the planes to meet in the middle; right?

[Strange]

How do the planes meet in the middle when the earth is moving 1,000 miles per hour away from the one plane? The speed of the earth will not allow the planes to meet in the middle; right?

 

What are you measuring the speed of the planes relative to?

 

What are you measuring the speed of the planes relative to?

 

What are you measuring the speed of the planes relative to?

[Questioning Physics]

As opposed to the planes not moving.

[swansont]

Please answer strange's question before proceeding. It is the crux of the issue. All speeds are measured relative to something else, often an object or sometimes an abstraction of a coordinate system. Saying "not moving" raises the same question. Not moving with respect to what?

[Questioning Physics]

The speed of the one place is relative towards going with the direction the earth is moving at 1,000 miles per hour and the speed of the other plane is relative towards the earth not moving at the 1,000 miles per hour because the earth only move in one direction.

[Strange]

The speed of the one place is relative towards going with the direction the earth is moving at 1,000 miles per hour and the speed of the other plane is relative towards the earth not moving at the 1,000 miles per hour because the earth only move in one direction.

 

Do you want to try that again. In English.

[pzkpfw]

Go outside and face West.

 

Jump 1 metre forward.

 

Turn around (to the East).

 

Jump 1 metre forward (back to where you came from).

 

Was there any difference in your two jumps?

 

Are you Superman, and was one of your jumps 1,000 miles per hour (as you measure it) "faster" than the other?

[elfmotat]

You don't seem to understand what the words "relative to" mean. You can't just say, "Bob is moving fast." You have to say, "Bob is moving fast relative to Alice."

Why do we need this extra information? Well, the speed of Bob relative to Bob is zero! If Bob tosses a ball, the speed of Bob relative to Alice is not the same as the speed of Bob relative to the ball, etc.

You can't just say that a plane is moving at 400 mph, you need to specify what the plane is moving relative to. This is precisely where your confusion is coming from. There is no such thing as absolute speed, only speed measured relative to something else.

Edited October 28, 2014 by elfmotat