JEE MAIN - Physics (2006 - No. 28)
A force of $$ - F\widehat k$$ acts on $$O,$$ the origin of the coordinate system. The torque about the point $$(1, -1)$$ is
$$F\left( {\widehat i - \widehat j} \right)$$
$$ - F\left( {\widehat i + \widehat j} \right)$$
$$F\left( {\widehat i + \widehat j} \right)$$
$$ - F\left( {\widehat i - \widehat j} \right)$$
Giải thích
We know, Torque $$\overrightarrow \tau = \overrightarrow r \times \overrightarrow F $$
$$= \left( {\widehat i - \widehat j} \right) \times \left( { - F\widehat k} \right) $$
$$= F\left( {\widehat i + \widehat j} \right)$$
$$= \left( {\widehat i - \widehat j} \right) \times \left( { - F\widehat k} \right) $$
$$= F\left( {\widehat i + \widehat j} \right)$$