Answer: 3m - 6m = -3m (in z-direction).
- A 3m - 6m = -3m (in z-direction)
- B 3m, taking mainly the first term of the position-velocity cross product
- C 6m, taking mainly the second term of the position-velocity cross product
- D 0, mistakenly assuming the velocity and position vectors are parallel here
Correct answer: A. 3m - 6m = -3m (in z-direction)
Explanation: L = m(r × v). v = (2t, 3). At t=1: r = (1,3), v = (2,3). L<sub>z</sub> = m(rx vy - ry vx) = m(1×3 - 3×2) = m(3-6) = -3m.
Torque about axis O equals the force F multiplied by the perpendicular distance r⊥ from the axis to the line of action of the force, producing rotation.
Concept context
Moment of inertia, torque, angular momentum, rolling motion. Very high JEE weightage.
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