## Essential University Physics: Volume 1 (3rd Edition)

We know that $v=\frac{l}{t}$ and that v is equal to $\sqrt{\frac{F}{\frac{m}{l}}}$. Thus, we combine these equations to find: $m = \frac{Ft^2}{l} = \frac{78.6\times.585^2}{18.3} = 1.47 \ kg$