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A man leaves from his home. He first walks 40 meters in north-west direction and then 40 meters in south-west direction. Next he walks 40 meters in south-east direction. Finally, he turns towards his house. In which direction is he moving?

Solution

✅ Correct Option: 1

Let the starting position (home) be at the origin (0, 0).

Taking east as positive x-direction and north as positive y-direction.


After walking 40 meters in north-west direction:

North-west makes 45° with both north and west axes.

x-displacement: −40cos⁡(45°)=−40×12=−202-40 \cos(45°) = -40 \times \dfrac{1}{\sqrt{2}} = -20\sqrt{2}

y-displacement: 40sin⁡(45°)=40×12=20240 \sin(45°) = 40 \times \dfrac{1}{\sqrt{2}} = 20\sqrt{2}

Position: (−202,202)(-20\sqrt{2}, 20\sqrt{2})


After walking 40 meters in south-west direction:

South-west makes 45° with both south and west axes.

Additional x-displacement: −40cos⁡(45°)=−202-40 \cos(45°) = -20\sqrt{2}

Additional y-displacement: −40sin⁡(45°)=−202-40 \sin(45°) = -20\sqrt{2}

Position: (−202−202,202−202)=(−402,0)(-20\sqrt{2} - 20\sqrt{2}, 20\sqrt{2} - 20\sqrt{2}) = (-40\sqrt{2}, 0)


After walking 40 meters in south-east direction:

South-east makes 45° with both south and east axes.

Additional x-displacement: 40cos⁡(45°)=20240 \cos(45°) = 20\sqrt{2}

Additional y-displacement: −40sin⁡(45°)=−202-40 \sin(45°) = -20\sqrt{2}

Final position: (−402+202,0−202)=(−202,−202)(-40\sqrt{2} + 20\sqrt{2}, 0 - 20\sqrt{2}) = (-20\sqrt{2}, -20\sqrt{2})


To return home, he needs to go from (−202,−202)(-20\sqrt{2}, -20\sqrt{2}) to (0,0)(0, 0).

Required displacement:

x-direction: 0−(−202)=2020 - (-20\sqrt{2}) = 20\sqrt{2} (positive, towards east)

y-direction: 0−(−202)=2020 - (-20\sqrt{2}) = 20\sqrt{2} (positive, towards north)

Since both displacements are equal and positive, the direction is north-east.

Therefore, the answer is Option 1: North-east.

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