Why is the handle of a screwdriver made long to rotate a screw?

$A$ force $\vec{F}=(2 \hat{i}+3 \hat{j}-5 \hat{k}) \, N$ acts at a point $\vec{r}_1=(2 \hat{i}+4 \hat{j}+7 \hat{k}) \, m$. The torque of the force about the point $\vec{r}_2=(\hat{i}+2 \hat{j}+3 \hat{k}) \, m$ is ............. $N m$.

Four forces are applied to a wheel of radius $10\,cm$ as shown in the figure. The net torque produced by all these forces about $C$ is

$A$ person supports a book between his finger and thumb as shown (the point of grip is assumed to be at the corner of the book). If the book has a weight of $W$,then the person is producing a torque on the book of

$A$ force of $3\hat{i} + 2\hat{j} - \hat{k} \text{ N}$ acts on a particle with position vector $\hat{i} + \hat{j} - \hat{k} \text{ m}$. The magnitude of torque of the given force is

$A$ force $\vec{F} = 4\hat{i} - 3\hat{j} + 4\hat{k} \, N$ acts on a particle at a position $\vec{r} = 3\hat{i} + 2\hat{j} + 3\hat{k}$ from the origin. The torque acting on the particle is: