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?
Given diameter of wheel of bus = d = 140 cm
Speed of bus = 72.6 km/hr
∴ Distance covered by bus in one hour = 72.6 km = 7260000 cm
Distance covered in one minute = 121000 cm → eqn1
Let the number of revolutions made by wheel per minute = x
Distance covered by wheel in one revolution = circumference of wheel = 2πR
Distance covered by wheel in one revolution = 2π(70)
(putting value of R)
= 2×22×10 = 440 cm
∴ Total distance = No. of revolution× Distance covered in1 revolution
On putting the required values we get,
121000 = 440×(x)
⇒ x = 275
Number of revolutions made per minute is 275.
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