The equation relating angular speed and linear speed is:
v = r w
where,
v = linear speed
r = radius = 0.5 diameter = 6 cm
w = angular speed in rad
First let us convert w in rad / minute:
w = 7200 rev / min * (2π rad / 1 rev)
w = 45,238.93 rad / min
So linear speed is therefore calculated as:
v = (6 cm) (45,238.93 rad / min)
v = 271,433.60 cm / min
or expressed in other units:
v = 4,523.90 cm / s = 45.24 m / s = 2,714.34 m / min