Find the torque of a force F→ = -3î + ĵ

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Find the torque of a force F^{^→} = -3î + ĵ + 5k̂ acting at the point r^{^→} = 7î + 3ĵ + k̂.

1. -21î + 3ĵ - 5k̂
2. -14î + 3ĵ + 16k̂
3. 4î - 4ĵ + 6k̂
4. 14î - 38ĵ + 16k̂

Correct Option: D

F^{^→} = -3î + ĵ + 5k̂ ; r^{^→} = 7î + 3ĵ + k̂
Torque (τ^{^→}) = r^{^→} × F^{^→}
= (7î + 3ĵ + k̂ ) × (-3î + ĵ + 5k̂)
= 7k̂ + 35(-ĵ) - 9(-k̂) + 15î - 3ĵ + (-î)
= -14î - 38ĵ + 16k̂