Question

The wheels of a car are of diameter $80$ cm each. How many complete revolutions does each wheel make in $10$ minutes when the car is travelling at a speed of $66$ km per hour

Answer 1

Now,

Diameter of wheel $\left(D\right)=80$ cm

Radius $\left(r\right)=\frac{80}{2}=40$ cm.

$1$ complete revolution of wheel = Circumference of wheel

Circumference of wheel $=2\pi r=2\pi \times 40=80\pi$ cm or $0.8\pi$ m

Speed of the car $=66$ km per hr $=\frac{66\times 1000}{60}$ m per min.

$\therefore$ Speed of the car $=1100$ m / min.

Therefore, in $10$min, the car will travel a distance of $1100\times 10=11000$ m

No. of revolutions of wheel $=\frac{11000}{0.8\pi }=\frac{11000\times 7}{0.8\times 22}=4375$

Each wheel of the car makes $4375$ complete revolutions in $10$ mins.