/*! 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 33 A spelumker is surveying a cave.... [FREE SOLUTION] | 91Ó°ÊÓ

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A spelumker is surveying a cave. She follows a passage 180 \(\mathrm{m}\) straight west, then 210 \(\mathrm{m}\) in a direction \(45^{\circ}\) east of south, and then 280 \(\mathrm{m}\) at \(30^{\circ}\) east of north. After a fourth unmeasured displacement, she finds herself back where she started. Use a scale drawing to determine the magnitude and direction of the fourth displacement. (See also Problem 1.73 for a different approach to this problem.)

Short Answer

Expert verified
The fourth displacement is 143.44 m at an angle of 40.15° south of west.

Step by step solution

01

Analyze the First Movement

The spelunker travels 180 m straight west. In our coordinate system, west corresponds to the negative x-axis. Thus, the displacement vector for this movement is \((-180 \text{ m}, 0 \text{ m})\).
02

Analyze the Second Movement

The next movement is 210 m at an angle of \(45^{\circ}\) east of south. We can break this down into components using trigonometry:- Southward (negative y-direction): \(210 \cos(45^{\circ}) = 148.5 \text{ m}\)- Eastward (positive x-direction): \(210 \sin(45^{\circ}) = 148.5 \text{ m}\)This results in the displacement vector \((148.5 \text{ m}, -148.5 \text{ m})\).
03

Analyze the Third Movement

The spelunker then travels 280 m at \(30^{\circ}\) east of north. Similarly, we find the components:- Northward (positive y-direction): \(280 \cos(30^{\circ}) = 242.49 \text{ m}\)- Eastward (positive x-direction): \(280 \sin(30^{\circ}) = 140 \text{ m}\)Thus, the displacement vector is \((140 \text{ m}, 242.49 \text{ m})\).
04

Sum the Vectors

Add all the displacement vectors to find the resultant vector. This will give the total position from the start before the fourth displacement:- Total x-component: \(-180 + 148.5 + 140 = 108.5 \text{ m}\) (east)- Total y-component: \(0 - 148.5 + 242.49 = 93.99 \text{ m}\) (north)The result is \((108.5, 93.99)\).
05

Calculate the Fourth Displacement

Since the spelunker returns to her starting point, the fourth displacement must negate the resultant vector from Step 4. Therefore, the fourth vector is \((-108.5, -93.99)\). Convert these into magnitude and direction:- Magnitude: \(\sqrt{(-108.5)^2 + (-93.99)^2} \approx 143.44 \text{ m}\)- Direction: \(\tan^{-1}\left(\frac{-93.99}{-108.5}\right) \approx 40.15^{\circ}\) south of west.

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Key Concepts

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

Displacement Vectors
In the context of vector addition, displacement vectors are crucial in describing movement across a plane. A displacement vector details both the magnitude and direction from one point to another. When a spelunker or any other individual is navigating a space, these vectors help track their precise location changes. Displacement vectors are useful because they give a complete picture of movement without needing to know the path taken between the start and end points. Each movement or leg of the journey can be represented as a vector with specific components along an axis, like moving west, east, north, or south in a cave system. By combining these vectors, we obtain a resultant vector representing the total change in position. If several movements eventually bring you back to your starting point, the resultant vector would be nullified by the final movement, effectively balancing it out.
Trigonometry
Trigonometry is indispensable in breaking down vectors into their components, especially when the vectors are not aligned with the main axes. Components are the projections of the vector along the x and y axes and are found using trigonometric functions like sine and cosine.For example, when the spelunker moves 210 m at an angle of 45° east of south, we can use trigonometry to break this movement into:\[\text{South component (y)} = 210 \times \cos(45^{\circ}) \approx 148.5 \, \text{m} \\text{East component (x)} = 210 \times \sin(45^{\circ}) \approx 148.5 \, \text{m} \]This process is repeated with each movement, turning vectors into manageable parts that can be easily summed. By mastering trigonometry, you can interpret, decompose, and reassemble vectors in various directions, making it easier to solve complex spatial problems.
Scale Drawing
Scale drawings are an essential tool for visualizing problems involving vectors, especially when dealing with directions and angles. By using a consistent scale, you can create a scaled-down version of the problem, making it easier to understand and solve. A scale drawing allows you to represent each vector's direction and magnitude visually. For example, using a paper to draw the vectors the spelunker followed allows you to lay out the cave survey. These drawings help you estimate the final displacement needed to return to the starting point. While computing the final answer mathematically is precise, a scale drawing provides intuitive insight and can make complex vector problems feel more tangible. When vectors are plotted accurately, the fourth vector—which returns the spelunker to her starting point—becomes apparent by simply measuring on the drawing and using it for a more visual confirmation.

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Most popular questions from this chapter

You are camping with two friends, Joe and Karl. Since all three of you like your privacy, you don't pitch your tents close together. Joe's tent is 21.0 \(\mathrm{m}\) from yours, in the direction \(23.0^{\circ}\) south of east. Karl's tent is 32.0 \(\mathrm{m}\) from yours, in the direction \(37.0^{\circ}\) north of east. What is the distance between Karl's tent and Joe's tent?

Bones and Muscles A patient in therapy has a forearm that weighs 20.5 \(\mathrm{N}\) and that lifts a \(112.0-\mathrm{N}\) weight. These two forces have direction vertically downward. The only other significant forces on his forearm come from the biceps muscle (which acts perpendicularly to the forearm) and the force at the elbow. If the biceps produces a pull of 232 \(\mathrm{N}\) when the forearm is raised \(43^{\circ}\) above the horizontal, find the magnitude and direction of the force that the elbow exerts on the forearm. (The sum of the elbow force and the biceps force must balance the weight of the arm and the weight it is carrying, so their vector sum must be 132.5 \(\mathrm{N}\) , upward.)

A ship leaves the island of Guam and sails 285 \(\mathrm{km}\) at \(40.0^{\circ}\) north of west. In which direction must it now head and how far must it sail so that its resultant displacement will be 115 \(\mathrm{km}\) directly east of Guam?

You are hungry and decide to go to your favorite neighbor- hood fast-food restaurant. You leave your apartment and take the elevator 10 flights down (each flight is 3.0 \(\mathrm{m}\) ) and then go 15 \(\mathrm{m}\) south to the apartment exit. You then proceed 0.2 \(\mathrm{km}\) east, turn north, and go 0.1 \(\mathrm{km}\) to the entrance of the restaurant. (a) Determine the displacement from your apartment to the restaurant. Use unit vector notation for your answer, being sure to make clear your choice of coordinates. (b) How far did you travel along the path you took from your apartment to the restaurant, and what is the magnitude of the displacement you calculated in part (a)?

Starting with the definition 1 in. \(=2.54 \mathrm{cm},\) find the number of (a) kilometers in 1.00 mile and (b) feet in 1.00 \(\mathrm{km}\) .

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