Question

A force of `-Fhatk` acts on O, the origin of the coodinate system. The torque about the point (1,-1) is

A. `-F (hati + hatj)`
B. `F (hati + hatj)`
C. `-F (hati - hatj)`
D. `F (hati - hatj)`

Answer 1

Correct Answer - B
Here, `overset rarr(F) =- F hatk`
`overset rarr(r ) = (hati - hatj)`
`overset rarr(tau) = overset rarr(r ) xx overset rarr(F) = (hati - hatj) xx (-F hatk)`
`-F (hati xx hatk - hatj xx hatk) = - F(-hatj - hati)`
`overset rarr(tau) = F (hati + hatj)`