Question

A wheel rotates making $20$ revolutions per second. If the radius of the wheel is $35 \,cm$, what linear distance does a point of its rim travel in three minutes? (Take $\left.\pi=\frac{22}{7}\right)$

• A. 7.92 km
• B. 7.70 km
• C. 7.80 km
• D. 7.85 km

Answer 1

Answer: (A)

Radius of the wheel $=35 \,cm$
$\therefore $ Circumference of the wheel $=2 \pi \times 35 \,cm$
$=2 \times \frac{22}{7} \times 35 \,cm =220 \,cm$
Hence, the linear distance travelled by a point of the rim in one revolution $=220\, cm$. Number of revolutions made by the wheel in 3 minutes $=20 \times 3 \times 60=3600$
$\therefore $ The linear distance travelled by a point of the rim in $3$ minutes $=220 \times 3600=792000 \,cm =7.92 ,\,km .$