a) Linear velocity, v = ωr ω = Angular velocity, r = radius.
ω = 40 revolutions per minute. 1 minute = (1/60) hour.
= 40*2π radians / (1/60) hour = 4800π radians per hour π = 3.14
= 4800*3.14 = 15072 radians / hour
but radius, r = 30 inches, 63360 inches = 1 mile, 30 inches = (30/63360) mile
Linear velocity, v = ωr
v = 15072 radians / hour * (30/63360) mile
v ≈ 7.136 miles / hour
b) Linear velocity, v = ωr
v = 8.9 radians/second * 20 cm
v = 178 cm/s