Question

A computerized spin balance machine rotates a 35-inch-diameter tire at 400 revolutions per minute.

(a) Find the road speed (in miles per hour) at which the tire is being balanced. (Round your answer to two decimal places.)

(b) At what rate should the spin balance machine be set so that the tire is being tested for 50 miles per hour? (Round your answer to two decimal places.)

Answer 1

2π*35*400 = 28000π in/min
Now just convert that to mi/hr.

for 50mi/hr, just take the fraction needed to get 50. That is, if the answer to (a) is 100 mi/hr, just take 50/100 of 400rpm to get the balancing speed.

Answer 2

circumference = pi d = 110 inches = 9.16 feet

it does 400 circumferences /minute
9.16 ft * 400 = 3665 feet/minute

3665 feet/min * 60 min/hr * 1 mi/5280 ft
= 41.65 miles/hr

400 * (50/41.65) = 480.19 rpm

Answer 3

dang - go with Damon again. I used a 35" radius.

Note to self: read twice, type once.

Answer 4

Thanks For your help with the 7 letter problem ! It was driving me crazy.