Answer
$1.3\times 10^{-54}kg$
Work Step by Step
First find the uncertainty in the energy of the free neutron from Eq. 28–2.
$$\Delta E \geq \frac{\hbar}{\Delta t}$$
Relate this to the mass uncertainty using equation 26–7.
$$\Delta E = (\Delta m)c^2$$
$$\Delta m \geq \frac{\hbar}{c^2 \Delta t}$$
$$=\frac{1.055\times 10^{-34}J \cdot s}{(3.00\times10^8m/s)^2(880s)}$$
$$=1.3\times 10^{-54}kg$$
