Question

A drive has a maximum speed of 10,000 revolutions per minute. If a disc has a diameter of 14 cm​, what is the linear​ speed, in​ km/h, of a point 6 cm from the center if the disc is spinning at a rate of 6000 revolutions per​ minute?

Answer 1

The point 6 cm away from the center travels in a circle of circumference 2π*(6 cm) = 12π cm, so that it covers this distance per revolution, 12π cm/1 rev.

So the disk has a linear speed of

(6000 rev/min) * (12π cm/rev) = 72,000π cm/min

which is equivalent to

(72,000π cm/min) * (1/100,000 km/cm) * (60 min/h)

or approximately 135.7 km/h.