Solution: As shown in the figure, AD is perpendicular to the ground in D and intersects with the arc in C, and BE is perpendicular to the ground in E. According to the topic, we know that BE=2, AC=3 and CD=0.5 (unit: meter). Let BG⊥AC be g, then AG = AD-GD = AC+CD-BE = 1.5.

( 120×π×3)/ 180=2π (m)。