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A steel bar with a radius of 6 inches is being ground in a lathe.
The surface speed of the bar is 29 ft/min. How many revolutions will the bar make in 51 sec?
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Let n be the number of revolutions per minute.
The diameter of the bar is d = 2*6 inches = 12 inches = 1 ft.
The surface speed of 29 ft/min is the circumference times the number
of revolution per minute, so we have this equation
29 = .
From this equation
n = = 9.231 revolutions per minute.
The number of revolution in 51 seconds is = 7.846 (rounded). ANSWER