Answer
1.59 cm.
Work Step by Step
The wave speed is given by $v=\lambda f$.
The maximum speed of particles on the cord is given by equation 11–7, $v_{max}=2\pi Af$. Set the two expressions equal to one another.
$$\lambda f = 2 \pi A f$$
$$A=\frac{\lambda}{2 \pi}=\frac{10.0\;cm}{2 \pi}=1.59\;cm$$
