Answer
$20$ cm
Work Step by Step
(c)
Using the same coordinate system$ defined in part (a)$, the hand starts pointing towards -y...
The initial position of the hand is now : $ \quad\vec{r_{1}}=(-10cm)\hat{j} $
and the final position:$ \quad\vec{r_{2}}=(10cm)\hat{j}$,
$\Delta\vec{r}=(10cm)\hat{j}-(-10cm)\hat{j}=(20cm)\hat{j}$
$|\Delta\vec{r}|=20$ cm
(two radii)
