revolutions per minute

Question

A car is moving at a rate of 28 miles per hour, and the diameter of its wheels is about 2 1/3 feet. Find the number of revolutions per minute the wheels are rotating.

Answer 1

A car is moving at a rate of 28 miles per hour, and the diameter of its wheels is about 2 1/3 feet. Find the number of revolutions per minute the wheels are rotating.

Given:

1. Speed = 28 miles/hour
2. 1 hour=60 minutes
3. Radius r=1.167 ft

Find the number of revolutions/ min:



Step 1: Convert speed to miles per minute

28 miles/hr= 28 miles/60 minutes=.4667 miles/minute

Step 2: Find circumference of a circle

C=2*∏*r=2*∏*(1.167 ft)=7.33ft

Step 3: convert feet to miles

.4667 miles/ min times 1 mile/5280 feet equal to .0013887

.4667miles/min divided by .0013887 miles/rev= 336 rev/ min