# A bicycle wheel, diameter 56 cm, is making 45 revolutions in every 10 seconds. At what speed, in kilometer per hour. Is the bicycle travelling?

2
by tkm

2016-02-18T14:55:15+05:30
Ok, here's what we got.

now, we are gonna find Periphery
Periphery=2πr
=(2)*(3.14)*(28)
=176 cms per rotation

so now it goes for 176 cms per rotation. and we are told about 45, so
according to the speed-distance/time, we must find the distance first.

Now it goes on 45 revolutions per 10 seconds that means it goes on 45*6 revolutions per 10*6 seconds, that means 270 revolutions per minute. and similarly to find the hour rate it goes on 270*60 rotation per hour [1 min*60]

that means it's going on 16200 revolutions per hour. Now multiply the 16200 with the Periphery.

=16200*176
=2851200 centimeters per hour.

Now convert the centimeters into kilometers, that means the answer is.... 28.512 kilometers per hour.

By the way, nice question. ^_^

I liked the way yoy answered.
thanks. ^_^
2016-02-18T16:45:42+05:30
Hello !
Diameter = 56 cm
radius = D / 2 = 28 cm
no. of revolutions (n) = 45
time ( t) = 10 sec
revolutions per second = 45 / 10 = 4.5 revolutions per second
Distance(D) covered per second = Perimeter of the wheel
× 4.5
Speed = Distance / Time
S = 2πr × 4.5
⇒ S = 176 cm × 4.5 per sec
⇒ S = 1.76 metre × 4.5 per sec
⇒ S = 7.920 metre/sec
Hence , The Speed is 7.920 m / sec.                          Ans.
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