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#cross product

19 public questions tagged with this topic.

A force F\=−3i^−4j^N acts at r\=2i^+5j^m. What is the magnitude of the torque about the origin?

τ = r×F = |i^j^k^250−3−40| = k^(2×(−4)−5×(−3)) = k^(−8+15) = 7k^Nm. Magnitude = 7Nm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 7 Nm. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

A force F\=−2i^+5j^N acts at r\=4i^−3j^m. What is the magnitude of the torque about the origin?

τ = r×F = |i^j^k^4−30−250| = k^(4×5−(−3)×(−2)) = k^(20−6) = 14k^Nm. Magnitude = 14Nm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 14 Nm. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

A 4kg particle moves with velocity v\=5j^m/s at r\=−3i^m. What is the magnitude of its angular momentum about the origin

L = r×p = |i^j^k^−300050| = k^((−3)×5−0×0) = −15k^kg m2/s. Magnitude = 15kg m2/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 15 kg m²/s. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

Vectors a\=4i^−2j^ and b\=3i^+5j^ are given. What is the direction of a×b?

a×b = |i^j^k^4−20350| = k^(4×5−(−2)×3) = k^(20+6) = 26k^. Direction is along the positive z-axis (k^). As per NCERT, applying relevant law/formula with correct units and sign convention leads to k^. This satisfies dimensional consistency and physical conditions given, so option D is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.