MCQ practice · SSC Physics Board questions · Chapter 2: Motion
What is the displacement of the boy?
Think it through first, then pick an option.
- a 28.28 m
- b 60 m
- c 94.248 m
- d 942.48 m
Answer and explanation
Correct answer: a 28.28 m
After three-quarters of a lap the start and end points are the ends of two perpendicular radii. Displacement = √(20² + 20²) = 28.28 m.
Why the other options are wrong
- b 60 m: 60 m = 3 × 20 comes from adding three radii. Displacement is measured along the straight line, not by adding radii.
- c 94.248 m: 94.248 m is ¾ × 2π × 20, that is the distance covered, not the displacement.
- d 942.48 m: 942.48 m is far too large. The displacement can never be greater than the diameter of the circle (40 m).
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