A boy is cycling in such a way that the wheels of his bicycle are making 140 revolutions per minute. If the diameter of a wheel is 60 cm, calculate the speed (in km/h) at which the boy is cycling.
Given diameter of wheel = d = 60 cm
Number of revolutions in one minute = 140
Number of revolutions in one hour = 140×60
Number of revolutions in one hour = 8400
Distance covered in one revolution = circumference of wheel
⇒ Distance covered in one revolution = πd
= 188.57 cm
Distance covered in one hour = Distance in 1 revolution × no. of revolutions
⇒ Total distance covered in one hour = 188.57× 8400
⇒ Total distance covered in one hour = 1583988 cm = 15.839 km
∴ speed with which boy is cycling = 15.839 km/hr
The speed with which boy is cycling is 15.839 km/hr