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Question
The diameter of a wheel is 0.70 m. Find the distance covered by it in 500 revolutions. If the wheel takes 5 minutes to make 500 revolutions; find its speed in :
(i) m/s
(ii) km/hr.
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Solution
Diameter = 0.70 m
Radius, r = 0.35 m
Distance covered in 1 revolution, i.e. circumference = 2πr = `2 xx 22/7 xx 0.35` = 2.20 m
Distance covered in 500 revolutions = 2.20 x 500 = 1100 m
Time taken = 5 minutes = 5 x 60 = 300 sec.
∴ Speed in m/s = `1100/300`
= `11/3 = 3 2/3` m/s
Again, Distance = 1100 m
= `1100/1000`
= `11/10` km
Time = 5 minutes
= `5/60` hr.
Speed in km/hr = `(11/10)/(5/60) = 11/10 xx 60/5`
= `66/5 = 13.2` km/hr.
Hence 1100 m, (i) `3 2/3` m/s (ii) 13.2 km/hr
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