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JEE Main202524 Jan 2025Evening ShiftPhysicsMotion in Two DimensionsActual

The position vector of a moving body at any instant of time is given as r = (5 t^2 i -5 t j ) m . The magnitude and direction of velocity at t=2 ~s is,

Options

  1. A5 15 ~m / s , making an angle of ⁻¹ 4 with - ve Y axis
  2. B5 15 ~m / s , making an angle of ⁻¹ 4 with + ve X axis
  3. C5 17 ~m / s , making an angle of ⁻¹ 4 with + ve X axis
  4. D5 17 ~m / s , making an angle of ⁻¹ 4 with - ve Y axis

Correct answer

D. 5 17 ~m / s , making an angle of ⁻¹ 4 with - ve Y axis

Step-by-step solution

aligned & r =5 t^2 i -5 t _ j & v =10 i -5 j & v =20 i -5 j at t =2 sec aligned aligned & = 20 5 =4 & = ⁻¹ 4 & From -veY-axis aligned

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