Practice question

Given: A force F = 7 i + 3 j N acts at r = -2 i + 1 j m . What is the magnitude of the torque about the origin? These values define the system as per NCERT data. Formula: tau = r × F = beginvmatrix i & j & k -2 & 1 & 0 7 & 3 & 0 endvmatrix = k ((-2) × 3 - 1 × 7) = k (-6 - 7) = -13 k Nm. This is standard NCERT relation. Substitution & Calculation: Magnitude = 13 Nm . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.