Answer:
10.8 km/hr
Explanation:
Given that
radius of the diameter is 4 cm
Converting 4 cm to km, we have
4/100000 = 0.00004 km or 4*10^-5 km
Angular speed is given as
v = 2πr/T
Where T is, 1/n,and n is the number of revolutions
v = (2 * 3.142 * 0.00004) / (1/7000)
v = 0.00126 / 0.007
v = 0.18 km/min
This is in km/min, now we convert to km/hr as requested.
0.18 * 60 = 10.8 km/hr