Did I answer this correctly? Trig rotation question

dpjwilson · #1 $Old$ April 26th, 2009, 09:21 PM

A car is traveling at 50 mph. Find the revolutions per minute of the wheels if the car tires have a 26 inch diameter.

50 mph , 13 inch radius
50 mph(5280ft in a mile)/60 min an hour = 4400 ft/min
total distance in 1 minute ---------------^

13 inches/12 inches in a foot * 2pi = 13pi/6 <--- 1 revolution

4400 ft/min / 13pi/6 = 646.41 rev per min

646.41 revolutions per minute? Did I do that right? Thank you for your help in advance.

Grandad · #2 $Old$ April 27th, 2009, 03:30 AM

Hello dpjwilson

Quote:

Originally Posted by dpjwilson $View Post$

A car is traveling at 50 mph. Find the revolutions per minute of the wheels if the car tires have a 26 inch diameter.

50 mph , 13 inch radius
50 mph(5280ft in a mile)/60 min an hour = 4400 ft/min
total distance in 1 minute ---------------^

13 inches/12 inches in a foot * 2pi = 13pi/6 <--- 1 revolution

4400 ft/min / 13pi/6 = 646.41 rev per min

646.41 revolutions per minute? Did I do that right? Thank you for your help in advance.

Looks good to me!

Grandad