Question

Difficulty: MediumScalars and Vectors

An aircraft flies due East at a velocity of 120 m/s120\text{ m/s} while a crosswind blows due North at 50 m/s50\text{ m/s}. What is the magnitude of the resultant velocity of the aircraft?

  1. 130 m/s130\text{ m/s}Answer
  2. B
    170 m/s170\text{ m/s}
  3. C
    70 m/s70\text{ m/s}
  4. D
    110 m/s110\text{ m/s}

Answer

The magnitude of the resultant velocity of the aircraft is 130 m/s130\text{ m/s}.
Because the aircraft's velocity and the wind's velocity are perpendicular to each other, their vector sum is found using the Pythagorean theorem R=v12+v22R = \sqrt{v_1^2 + v_2^2}. Substituting 120 m/s120\text{ m/s} and 50 m/s50\text{ m/s} gives R=1202+502=16900=130 m/sR = \sqrt{120^2 + 50^2} = \sqrt{16900} = 130\text{ m/s}.

Step-by-Step Solution

1
Identify the given velocity vectors and their relative direction.
Velocity due East ve=120 m/s\vec{v}_e = 120\text{ m/s} and velocity due North vn=50 m/s\vec{v}_n = 50\text{ m/s} are perpendicular to each other (9090^\circ angle).
East and North directions are orthogonal to each other.
2
Apply the Pythagorean theorem to calculate the magnitude of the resultant vector RR.
R=ve2+vn2=1202+502=14400+2500=16900=130 m/sR = \sqrt{v_e^2 + v_n^2} = \sqrt{120^2 + 50^2} = \sqrt{14400 + 2500} = \sqrt{16900} = 130\text{ m/s}.
The resultant of two perpendicular vectors forms the hypotenuse of a right-angled triangle.

Key Concept

Vector Addition of Perpendicular Vectors
Estimated Time:1m 0s
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