$\left(g=10 \,{m} / {s}^{2}\right)$
\(w _{ g }+ w _{ T }=\Delta K\)
\(- mgl \left(1-\cos 60^{\circ}\right)=\frac{1}{2} mv ^{2}-\frac{1}{2} mu ^{2}\)
\(v ^{2}= u ^{2}-2 gl \left(1-\cos 60^{\circ}\right)\)
\(v ^{2}=9-2 \times 10 \times 0.5\left(\frac{1}{2}\right)\)
\(v ^{2}=4\)
\(v =2 m / s\)