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A person walks in the following pattern: 3.1 km north, then 2.8 km west, and finally 5.7 km south. (a) How far and (b) at what angle (measured counterclockwise from east) would a bird fly in a straight line from the same starting point to the same final point?

Respuesta :

Answer:

a)  R = 3.82 m, b)  θ' = 222.9°

Explanation:

We can solve this displacement exercise using vectors, let us write the displacements in a Cartesian coordinate system, where the x-axis is in the East-West direction and the y-axis in the North-South direction

         d₁ = 3.1 j ^

         d₂ = -2.8 i ^

         d₃ = -5.7 j ^

We look for the displacements is each axis

X axis

         X = d₂

         X = -2.8 i ^

Y Axis

        Y = d₁ + d₃

        Y = 3.1 - 5.7

        Y = - 2.6 j ^

a) For total displacement let's use the Pythagorean theorem

          R = √ x² + y²

          R = √ 2.8² + 2.6²

          R = 3.82 m

b) for the angle we can use trigonometry

         tan θ = y / x

         θ = tan⁻¹ y / x

         θ = tan⁻¹ (-2.6 / -2.8)

         θ = 42.9°

 The angle respect to x axis is

         θ' = 180 + 42.9

        θ' = 222.9°