Answer
$2$
Work Step by Step
See Theorem $12.5 .2 b$
\[
\begin{array}{l}
\kappa(t)=\frac{\left\|\mathrm{r}^{\prime}(t) \times \mathrm{r}^{\prime \prime}(t)\right\|}{\left\|\mathrm{r}^{\prime}(t)\right\|^{3}} =\kappa(0)\\
\mathrm{r}^{\prime}(t) \times \mathrm{r}^{\prime \prime}(t)=\left|\begin{array}{ccc}
i & j & k \\
1 & 0 & 0 \\
1 & 2 & 0
\end{array}\right|=2 k \\
\kappa(0)=\frac{\|2 \mathrm{k}\|}{\|\mathrm{i}\|^{3}}=2
\end{array}
\]
