The wheel of a cart is making 5 revolutions per second. If the diameter of the wheel is 84 cm, find its speed in km per hour. [Take π = 22/7]


Diameter of the wheel = 84 cm


Let the radius of the wheel be R cm


Radius of the wheel = 84/2 cm = 42 cm


No. of revolutions wheel makes = 5 rev/sec


Since, 1 revolution = 2πR


Speed of the wheel = 5 × 2πR rev/sec


= 5 × 2 × 22/7 × 42 = 1320 cm/sec


= 13.20 m/sec


= 13.20 × 3600/1000 km/h


= 47.52 km/h


Since, 1 m/sec = 3600/1000 km/h


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