Question

61. Torque of a force F about O is defined as i=ixF. Here, i = OP as shown in figure.
p.
A force of (41+3+2K)N acts at point P(3, 4, 5) m. Find the torque of force about point o
(1,2,3) m.
(A) (-21 +492k)N-m
(B) (21 – 4+ 2k)N-m
(C)(-4i +2j – 2k)N-m
(D) Zero​

Answer 1

Answer:

B

Explanation:

I am assuming this force :

F = 4i+3j+2k

r = (3-1)i + (4-2)j + (5-3)k

= 2i + 2j + 2k

T = r × F

= (2i + 2j + 2k) × (4i+3j+2k)

= 6k - 4j - 8k + 4i +8j -6i

= -2k +4j - 2i

= -(2i - 4j + 2k)

(Minus sign is there because we have subtracted O's coordinates from P.