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JEE Main 2019 (11 Jan, Shift 2) · Equations of Kinematics

Equations of Kinematics question from JEE Main 2019 (11 Jan, Shift 2)

Q30JEE Main 2019 · 11 JAN · SHIFT 2Medium

Equations of Kinematics

A particle moves from the point (2.0i^+4.0j^)\left(2.0\hat{i} + 4.0\hat{j}\right) m, at t = 0, with an initial velocity (5.0i^+4.0j^)\left(5.0\hat{i} + 4.0\hat{j}\right) ms−1{}^{-1}. It is acted upon by a constant force which produces a constant acceleration (4.0i^+4.0j^)\left(4.0\hat{i} + 4.0\hat{j}\right) ms−2{}^{-2}. What is the distance of the particle from the origin at time 2 s?

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Answer: (b)

  1. r⃗=r⃗0+u⃗t+12a⃗t2\vec{r} = \vec{r}_0 + \vec{u}t + \frac{1}{2}\vec{a}t^2 with t=2 st = 2\text{ s}.
  2. x: 2+5(2)+12(4)(4)=20 m2 + 5(2) + \frac{1}{2}(4)(4) = 20\text{ m}; y: 4+4(2)+12(4)(4)=20 m4 + 4(2) + \frac{1}{2}(4)(4) = 20\text{ m}
  3. Distance from origin =202+202=202 m= \sqrt{20^2 + 20^2} = 20\sqrt{2}\text{ m}
  4. So the answer is (b) 20220\sqrt{2} m.
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