Question

M) a car is travelling at 29 mph. if the tires have a diameter of 25 inches, how fast are the cars tires turning? express answer in revolutions per minute

Answer 1

390 rpm

Explanation:

You want to know the speed in RPM of a 25-inch tire traveling 29 mph.

Feet per minute

At a speed of 29 miles per hour, the car is traveling ...

(29 mi/h)·(5280 ft/mi)(1 h/(60 min)) = 2552 ft/min

Feet per revolution

The circumference of the tire in feet is ...

C = πd

C = π(25 in)(1 ft/(12 in)) ≈ 6.54498 ft . . . . per revolution

RPM

The speed in RPM is ...

(2552 ft/min)/(6.54498 ft/rev) ≈ 389.917 rev/min

The tires are turning about 390 RPM.

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