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Static Helicopter Flights

by optoracko
Tags: flights, helicopter, static
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optoracko
#1
Feb24-10, 08:39 AM
P: 18
1. The problem statement, all variables and given/known data
How would a physics exper respond to the following suggestions made by three airline executives?

Executive A: Since the Earth rotates from west to east, we could operate static flights - helicopters that begin by hovering above new York City could begin their landing four hours later, when San Francisco arrives below.

Executive B: This could work for one way flights, but the return trip would take 20 hours.

Executive C: That will never work. It's like when you throw a ball up in the air, it comes back to the same point.

Executive A: That's only because the Earth's motion is not significant during that short a time.

2. Relevant equations

Speed = Distance / Time

3. The attempt at a solution

At first, I began by calculating the earth's rotation speed. I divided it's circumference at the equator, ~40,000 km by the time it takes for it to rotate once, 24 hours. I get the speed as 1667 km/h which converts to 463 m/s. I'm not quite sure how tackle this question. I'm thinking about looking for materials that say for how long the earth would need to rotate in order for it to be significant. I'm not sure if this is entirely correct, but also that the helicopter would need to maintain a certain height above the earth in order for the earth to have rotated enough before it lands to actually make a decent distance. Perhaps other factors could affect it was this height, such as air resistance, the strength of winds, and maybe even acceleration due to gravity. As such, things like the make of the helicopter and the amount of fuel that it has, or can hold may need to be changed.

I feel like I'm BSing quite a bit. I'm not sure if I'm interpreting this question correctly (i'm thinking that the helicopter levitates, stays for 4 hours and then lands directly below at a new place). I'm also not sure if the assumptions I'm making are correct.
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PhanthomJay
#2
Feb24-10, 10:37 AM
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Quote Quote by optoracko View Post
1. The problem statement, all variables and given/known data
How would a physics exper respond to the following suggestions made by three airline executives?

Executive A: Since the Earth rotates from west to east, we could operate static flights - helicopters that begin by hovering above new York City could begin their landing four hours later, when San Francisco arrives below.

Executive B: This could work for one way flights, but the return trip would take 20 hours.

Executive C: That will never work. It's like when you throw a ball up in the air, it comes back to the same point.

Executive A: That's only because the Earth's motion is not significant during that short a time.

2. Relevant equations

Speed = Distance / Time

3. The attempt at a solution

At first, I began by calculating the earth's rotation speed. I divided it's circumference at the equator, ~40,000 km by the time it takes for it to rotate once, 24 hours. I get the speed as 1667 km/h which converts to 463 m/s.
looks about right
I'm not quite sure how tackle this question. I'm thinking about looking for materials that say for how long the earth would need to rotate in order for it to be significant. I'm not sure if this is entirely correct, but also that the helicopter would need to maintain a certain height above the earth in order for the earth to have rotated enough before it lands to actually make a decent distance.
If a ball is thrown straight up in the air and it stays in the air for about 5 seconds, can you still catch it? The point on the earth's surface that you were standing on when you threw the ball, will have rotated about 2300 meters during that time, with respect to its center
Perhaps other factors could affect it was this height, such as air resistance, the strength of winds, and maybe even acceleration due to gravity. As such, things like the make of the helicopter and the amount of fuel that it has, or can hold may need to be changed.

I feel like I'm BSing quite a bit. I'm not sure if I'm interpreting this question correctly (i'm thinking that the helicopter levitates, stays for 4 hours and then lands directly below at a new place). I'm also not sure if the assumptions I'm making are correct.
What is the flaw in your line of reasoning??
mgb_phys
#3
Feb24-10, 10:44 AM
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P: 8,954
As a hint, your reasoning is flawed even without air/wind etc.
When the astronauts on the moon leaped into the air the moon didn't move under them.


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