Math Problem Statement

A plane is flying at 560 mph with a bearing of 300, degree300°. A wind is blowing at 20 mph with a bearing of 200, degree200°. Find the ground speed and actual direction of the airplane.

Solution

To solve the problem of finding the ground speed and actual direction of the airplane, we will use vector addition. The plane's velocity and the wind's velocity are combined to find the resultant vector, which represents the ground velocity.

Step 1: Represent the velocities as vectors

The velocity vectors will be represented in terms of their components in the north-east coordinate system:

  • Bearing 300300^\circ means 360300=60360^\circ - 300^\circ = 60^\circ west of north.
  • Bearing 200200^\circ means 200180=20200^\circ - 180^\circ = 20^\circ south of west.

Plane's velocity vector:

The magnitude is 560mph560 \, \text{mph}, and the bearing is 300300^\circ: Vplane=(560cos(300),560sin(300)).V_{\text{plane}} = (560 \cos(300^\circ), 560 \sin(300^\circ)). Using trigonometric values: cos(300)=cos(60)=0.5,sin(300)=sin(60)=32.\cos(300^\circ) = \cos(-60^\circ) = 0.5, \quad \sin(300^\circ) = \sin(-60^\circ) = -\frac{\sqrt{3}}{2}. Vplane=(560×0.5,560×32)=(280,484.12).V_{\text{plane}} = (560 \times 0.5, 560 \times -\frac{\sqrt{3}}{2}) = (280, -484.12).

Wind's velocity vector:

The magnitude is 20mph20 \, \text{mph}, and the bearing is 200200^\circ: Vwind=(20cos(200),20sin(200)).V_{\text{wind}} = (20 \cos(200^\circ), 20 \sin(200^\circ)). Using trigonometric values: cos(200)=cos(180+20)=cos(20),sin(200)=sin(180+20)=sin(20).\cos(200^\circ) = \cos(180^\circ + 20^\circ) = -\cos(20^\circ), \quad \sin(200^\circ) = \sin(180^\circ + 20^\circ) = -\sin(20^\circ). Approximating the trigonometric values: cos(20)0.9397,sin(20)0.3420.\cos(20^\circ) \approx 0.9397, \quad \sin(20^\circ) \approx 0.3420. Vwind=(20×0.9397,20×0.3420)=(18.79,6.84).V_{\text{wind}} = (20 \times -0.9397, 20 \times -0.3420) = (-18.79, -6.84).

Step 2: Add the velocity vectors

The ground velocity vector VgroundV_{\text{ground}} is the sum of the plane's and wind's velocity vectors: Vground=Vplane+Vwind.V_{\text{ground}} = V_{\text{plane}} + V_{\text{wind}}. Vground=(280+(18.79),484.12+(6.84)).V_{\text{ground}} = (280 + (-18.79), -484.12 + (-6.84)). Vground=(261.21,490.96).V_{\text{ground}} = (261.21, -490.96).

Step 3: Calculate the ground speed

The ground speed is the magnitude of the resultant vector: Ground speed=(261.21)2+(490.96)2.\text{Ground speed} = \sqrt{(261.21)^2 + (-490.96)^2}. Ground speed=68191.06+241043.32=309234.38.\text{Ground speed} = \sqrt{68191.06 + 241043.32} = \sqrt{309234.38}. Ground speed556.06mph.\text{Ground speed} \approx 556.06 \, \text{mph}.

Step 4: Find the actual direction

The actual direction is the angle of the resultant vector from the north, given by: θ=tan1(east componentnorth component).\theta = \tan^{-1}\left(\frac{\text{east component}}{\text{north component}}\right). θ=tan1(261.21490.96).\theta = \tan^{-1}\left(\frac{261.21}{-490.96}\right). θ=tan1(0.532).\theta = \tan^{-1}(-0.532). θ27.99.\theta \approx -27.99^\circ.

Since the angle is measured clockwise from north: Actual direction=36027.99=332.01.\text{Actual direction} = 360^\circ - 27.99^\circ = 332.01^\circ.

Final Answer:

  • Ground speed: 556.06mph556.06 \, \text{mph}.
  • Actual direction: 332.01332.01^\circ.

Would you like further clarification on any step?


5 Related Questions:

  1. How do you find the bearing if the wind direction changes?
  2. What happens to the ground speed if the wind speed increases?
  3. How would the calculations differ if the wind had a bearing of 00^\circ (north)?
  4. Why do we use vector addition to solve this type of problem?
  5. How would you calculate the airspeed if only the ground speed and wind speed were known?

Tip:

Always break velocity into components for easier calculation when working with bearings and directions!

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Math Problem Analysis

Mathematical Concepts

Vector Addition
Trigonometry
Coordinate Geometry

Formulas

V_{plane} = (v \cos(\theta), v \sin(\theta))
V_{ground} = V_{plane} + V_{wind}
Ground speed = \sqrt{(x_{component})^2 + (y_{component})^2}
Actual direction = \tan^{-1} \left( \frac{x_{component}}{y_{component}} \right)

Theorems

Vector Addition Theorem
Pythagorean Theorem
Trigonometric Identities

Suitable Grade Level

Grades 11-12