Finding the angle between a plumb line and the Earth's surface.

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Homework Help Overview

The discussion revolves around calculating the angle between a plumb line and the Earth's surface, specifically in the context of a plane flying over the North Pole. The subject area includes concepts from dynamics and rotational motion.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of Newton's second law and the relationship between tension, acceleration, and gravitational force. There are attempts to equate forces to derive the angle using trigonometric functions. Questions arise regarding discrepancies between calculated values and those provided in a textbook.

Discussion Status

Participants are examining the calculations and questioning the assumptions made in the textbook. Some guidance is provided in the form of agreement on the correctness of a participant's calculations, though no consensus is reached regarding the textbook's values.

Contextual Notes

There is mention of potential omissions in the textbook calculations, specifically regarding the value of π, which may affect the results. The discussion reflects uncertainty about the accuracy of both the participant's and the textbook's calculations.

andyonassis
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Homework Statement
A plane flies across the north pole at 223.52 m/s, following a meridian of longitude (which rotates around the earth). Find the angle between the direction of a plumb line hanging freely as it passes over the pole and one hanging freely at the surface of the earth over the pole.
Relevant Equations
F = ma
$$\omega = \frac{2\pi}{T} $$
From Newton's second law:
$$T_{x} = F_{turn}$$
So
$$T \sin \theta = ma$$
$$T_{y} = F_{y}$$
so
$$T \cos \theta = mg$$
Equate the two equations to get:
$$ \frac{T \sin \theta}{a} = \frac{T \cos \alpha}{g} $$
and the angle is given by:
$$tan (\theta) = \frac{a}{g} $$
where ##r = \frac{v}{w}## and ##a = r\omega^{2}##
From this we get:
$$\theta = arctan(\frac{v\omega}{g}) = arctan(\frac{223.52}{9.8} \times \frac{2\pi}{24\times 60 \times 60}) = 1.65 \times 10^{-3} radians$$

However, the book says ##\omega = 2.31 \times 10^-4 rad/s## so ##\theta = 5.25 \times 10^{-4}##radians.
 
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andyonassis said:
Homework Statement:: A plane flies across the north pole at 223.52 m/s, following a meridian of longitude (which rotates around the earth). Find the angle between the direction of a plumb line hanging freely as it passes over the pole and one hanging freely at the surface of the Earth over the pole.
Relevant Equations:: F = ma
$$\omega = \frac{2\pi}{T} $$

From Newton's second law:
$$T_{x} = F_{turn}$$
So
$$T \sin \theta = ma$$
$$T_{y} = F_{y}$$
so
$$T \cos \theta = mg$$
Equate the two equations to get:
$$ \frac{T \sin \theta}{a} = \frac{T \cos \alpha}{g} $$
and the angle is given by:
$$tan (\theta) = \frac{a}{g} $$
where ##r = \frac{v}{w}## and ##a = r\omega^{2}##
From this we get:
$$\theta = arctan(\frac{v\omega}{g}) = arctan(\frac{223.52}{9.8} \times \frac{2\pi}{24\times 60 \times 60}) = 1.65 \times 10^{-3} radians$$

However, the book says ##\omega = 2.31 \times 10^{-5}## rad/s so ##\theta = 5.25 \times 10^{-4}##radians.
Whoever did the calculation for the book left out π.
 
haruspex said:
Whoever did the calculation for the book left out π.
so my answer isn't technically wrong?
 
andyonassis said:
so my answer isn't technically wrong?
Your answer looks right to me.
 

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