A drone flies 40 km East, then 21 km South, then 28 km West, then 16 km North. Calculate the magnitude of its displacement from the launch point.

Last Updated: 07 Sept 2026

A15 km

B13 km

C11 km

D105 km

Correct Answer: 13 kmYour Answer: B

Explanation

Step 1: Mark the starting point as O(0,0) and choose East as +x and North as +y. | Step 2: Horizontal calculation: +40 + −28 = 12 km; hence the final point is east of O by 12 km. | Step 3: Vertical calculation: −21 + +16 = -5 km; hence it is south of O by 5 km. | Step 6: The total route is 105 km, but that is not the required shortest distance; the direct displacement is 13 km.

Important Notes

Separate total path length from displacement; the question asks for the straight-line gap between start and finish. |
Use East = +x, West = −x, North = +y and South = −y. |
A route may be long while its displacement is small, so never add every segment unless total distance is requested. |
Estimate the answer before selecting an option: the displacement must be less than or equal to the route length. |

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A drone flies 40 km East, then 21 km South, then 28 km West, then 16 km North. Calculate the magnitude of its displacement from the launch point.

Explanation

Important Notes

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