Now to solve this problem, all we have to remember is the
formula for calculating the linear speed given the radial speed, that is:
v = r w
where,
v = is the linear velocity or linear speed
r = is the radius of the circular disk = (1 / 2) diameter
= (1/ 2) (2.5 inches) = 1.25 inches
w = is the radial velocity (must be in rad per time) =
7200 rev per minute
Calculating for v:
v = 1.25 inches (7200 rev per minute) (2 π rad / 1 rev)
v = 56,548.67 inches / minute
Converting to miles per hour:
v = 56,548.67 inches / minute (1 mile / 63360 inches) (60
min / hour)
v = 53.55 mile / hour
