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NTA Abhyas JEE Main2020PhysicsMotion in Two DimensionsPractice

The position vector of a particle is determined by the expression r → = 2 t 2 i ^ + 3 t j ^ + 9 k ^ . The magnitude of its displacement (in m ) in first two seconds is

Correct answer

10

Step-by-step solution

r → = 2 t 2 i ^ + 3 t j ^ + 9 k ^ At t = 0 , r 1 → = 9 k ^ At t = 2 s , r 2 → = 8 i ^ + 6 j ^ + 9 k ^ ∴ Δ r → = r 2 → - r 1 → = 8 i ^ + 6 j ^ ∴ Δ r → = r 2 → - r 1 → = 8 2 + 6 2 = 10 m

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