/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 39 Canadian geese migrate essential... [FREE SOLUTION] | 91Ó°ÊÓ

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Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 \(\mathrm{km} / \mathrm{h}\) . If one such bird is flying at 100 \(\mathrm{km} / \mathrm{h}\) relative to the air, but there is a 40 \(\mathrm{km} / \mathrm{h}\) wind blowing from west to east, (a) at what angle relative to the north-south direction should this bird head so that it will be traveling directly southward relative to the ground? (b) How long will it take the bird to cover a ground distance of 500 \(\mathrm{km}\) from north to south? (Note: Even on cloudy nights, many birds can navigate using the earth's magnetic field to fix the north-south direction.)

Short Answer

Expert verified
(a) \( 23.58^\circ \) west of south, (b) 5.44 hours.

Step by step solution

01

Understand the problem

The bird is flying with a speed of 100 km/h relative to the air, but the air (wind) is moving at 40 km/h from west to east. We need to find the angle, \( \theta \), at which the bird should head to maintain a direct southward motion. Then, we need to calculate the time taken to cover 500 km southwards on the ground.
02

Set up the vector components for the velocities

Represent the bird's velocity as a vector: \( \vec{v_b} \), with magnitude 100 km/h. The wind velocity \( \vec{v_w} \) is 40 km/h east. To head directly south, the bird's eastward component of velocity must cancel out the wind's velocity. The bird's southward component must do the actual work of moving south.
03

Calculate the required heading angle

Let the heading of the bird make an angle \( \theta \) with the south (Y-axis). The eastward (X-axis) component of the bird's velocity is \( 100 \sin \theta = 40 \). Solving for \( \theta \), we have:\[ 100 \sin \theta = 40 \]\[ \sin \theta = 0.4 \]\[ \theta = \arcsin(0.4) \approx 23.58^\circ \]
04

Calculate the southward velocity component

Now, calculate the southward (Y-axis) component of the bird's velocity. This is given by:\[ v_{b_y} = 100 \cos \theta \]Plug \( \theta \approx 23.58^\circ \) into the equation:\[ v_{b_y} = 100 \cos(23.58^\circ) \approx 91.92 \text{ km/h} \]
05

Calculate the time to travel 500 km south

Using the southward component of the velocity, calculate the time \( t \) taken to travel 500 km:\[ t = \frac{500}{v_{b_y}} = \frac{500}{91.92} \approx 5.44 \text{ hours} \]
06

Conclusion

The bird should head approximately \( 23.58^\circ \) west of south to compensate for the eastward wind. At this heading, it will take about 5.44 hours to travel 500 km directly south on the ground.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Wind Influence on Flight Path
When Canadian geese migrate, they often encounter winds that can alter their flight path. The wind, particularly when blowing from the west to the east, affects the bird's trajectory. Imagine flying an airplane; if there's a crosswind, you'll need to adjust your direction to reach your destination directly. Similarly, a bird must compensate for the wind's influence.
To fly directly south despite an eastward wind, a bird needs to head slightly westward. This adjustment ensures that the influence of the wind is neutralized, and the net flight direction remains southwards. This concept is crucial for migrating birds, as it allows them to maintain a straight path rather than veering off-course.
In our problem, a 40 km/h wind from west to east affects the bird's flight. Therefore, the bird needs to alter its flight direction to ensure it stays on the intended north-south path.
Vector Components
Understanding vector components is key for analyzing motion, especially when dealing with multiple influences like wind and bird flight. A vector is an arrow; it has both direction and magnitude. In our scenario, two vectors affect the bird's motion: the bird's own velocity and the wind's velocity.
Each vector can be split into horizontal and vertical components. For the bird, its heading makes an angle with the desired southward path. The velocity vector is decomposed into:
  • Eastward (or X-axis) component
  • Southward (or Y-axis) component
The goal is for the eastward component of the bird’s velocity to cancel out the wind’s eastward pull. By determining these components, you can figure out the exact direction the bird should fly to reach its destination directly south.
Trigonometric Functions
Trigonometric functions such as sine and cosine play a crucial role in resolving vector components. In physics, these functions help in breaking down vectors based on an angle.
The problem involves calculating the angle, \( \theta \), using the sine function. Since the sine of the angle gives the ratio of the opposite side to the hypotenuse in a right-angled triangle, the eastward component (which must cancel out the wind) is obtained with \( 100 \sin \theta \). Here, 100 km/h is the bird's speed relative to air, and we solve for \( \theta \) using: \[\sin \theta = 0.4\]This angle adjustment allows the bird to maintain a southern trajectory by compensating for wind deviation.
Once the angle is known, the cosine function can help find the southward component of the bird's velocity, ensuring the correct direction for its migration.
Physics of Bird Migration
The physics of bird migration involves strategy and natural navigation. Birds utilize both environmental cues and internal mechanisms to navigate their thousands of kilometers migration patterns.
  • Environmental factors: Birds use the Earth's magnetic field, stars, and sun to guide them.
  • Internal mechanisms: Internal biological clocks help in timekeeping for seasonal migration.
In this exercise, the bird's intended migration path is affected by wind, showing how external forces can influence navigation. Birds adapt by adjusting their heading to counteract these forces, showcasing an inherent understanding of vector principles, even if subconsciously.
Understanding the physics behind such movements aids in appreciating these incredible feats of nature and the sophisticated means by which birds traverse great distances successfully.

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