The radius of the wheel of a vehicle is 35 cm. The wheel makes 10 revolutions in 6 seconds. The speed of the vehicle is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 13.2 km/hr
In one revolution the wheel rolls forward by its circumference, \(2\pi r\), so the vehicle’s distance = revolutions × circumference.
Circumference of the wheel \(\displaystyle =2\times\frac{22}{7}\times35=220\) cm
Distance in 6 seconds \(=10\times220=2200\) cm \(=22\) m
Speed in metres per second \(\displaystyle =\frac{22}{6}\)
Converting to km/hr (1 m/s = 18/5 km/hr): \(\displaystyle \frac{22}{6}\times\frac{18}{5}=\frac{396}{30}=\) 13.2 km/hr