A cup anemometer is used to measure wind speed, under assumptionthat the speed of rotation of the anemometer is proportional to thespeed of air flow that forces the cups to rotate. The cups catchthe wind, and spin around a total rotational distance that isdivided by a length of time to determine the wind’s speed. Thisinstrument is typically used on fixed weather stations because thewind direction does not affect the air flow rate, since the cupsare oriented in different directions. First, it is necessary tomeasure the rotational distance of the cup. This is determinedusing the radius (r) measured from the cup’s propeller arm to thecentral rod of rotation.

Then, use the formula for a circles circumference, 2r to findthe distance of one rotation by the cup anemometer (use d = 3.14).Next, multiply by circumference by the number of rotations thatoccurred over a period of time, to find the total rotationaldistance. Lastly, divide the total rotational distance by theamount of time to solve for wind speed. Determine the wind speed inmeters per second for a cup anemometer with radius of 11 cm whenthere were 67 rotations recorded in 30 seconds. What is theequivalent wind speed in miles per hour? Show calculation.