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Question
The diameter of the wheels of a bus is 140 cm. How many revolutions per minute do the wheels make when the bus is moving at a speed of 72.6 km per hour?
Solution
Diameter of the wheel = 140 cm
Radius = 70 cm
Circumference = 2πr
`=2xx22/7xx70`
= 440 cm
Speed of the wheel = 72.6 km per hour
Distance covered by the wheel in 1 minute `=(72.6xx1000xx100)/60 = 121000 "cm"`
Number of revolutions made by the wheel in 1 minute` ="Total distance covered"/"Circumference"`
`=121000/440`
= 275
Hence, the wheel makes 275 revolutions per minute.
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