The tires on an automobile have a radius of 0.36 meters. If the tires make 11 revolutions per second, find the speed of the car in kilometers per hour (kph). Round to the nearest tenth. [1 km = 1000 m and 1 hr = 3600 s]
A) 89.6 kph
B) 44.8 kph
C) 14.3 kph
D) 28.5 kph

Question

Quizplus · Accepted Answer

Each revolution of the tire covers a distance equal to the circumference of the tire. The circumference can be found by multiplying the radius by 2π. 
Circumference = 2π × 0.36 = 2.26 meters 
Therefore, each revolution covers 2.26 meters. 
If the tire makes 11 revolutions per second, the distance covered by the tire in 1 second is: 
Distance = 11 rev/s × 2.26 m/rev = 24.86 m/s 
To convert m/s to km/h, we need to multiply by 3.6. 
Speed = 24.86 m/s × 3.6 km/h/m/s = 89.5 kph (rounded to the nearest tenth)

Therefore, the best choice is A.

The Tires on an Automobile Have a Radius of 0