Agirl on a swing varies in height from 60 cm above the ground to 180 cm. the girl's greatest velocity

Use mechanical energy conservation

[Ek + Ep] at lower point = [Ek + Ep] at higher point

Ek at lower point = Ek at higher point + Ep at higher point - Ep at lower point

Ek at lower point = 1/2 m v^2

Ek at higher point = 0

Ep at higher point - Ep at lower point = mg(1.80m -0.60m)

1/2 mv^2 = mg (1.20m)

v^2 = 2g(1.20m)

use g = 10m/s^2

v = √[(2)(10m/s^2)(1.20m)] = 4.90 m/s^2

Iknow the first part it is the average star i am not 100% sure