A compact disk is 12 cm in diameter and rotates at 100 rpm (revolutions per minute) when being played. The hole in the center is 1.5 cm in diameter. Find the speed in cm/min of a point on the outer edge of the disk and the speed of a point on the inner edge.
+23254 The formula for the circumferende of a circle is: C = π·d
At the outer edge: C = π·d = π·12 = 12π cm
A point on the outer edge travels 12π cm each revolutions, so, in 100 revolutions, it travels
100 times 12π = 1200π cm; so its speed is 1200π cm/min
If you want, you can turn this into a decimal equivalent.
To find the speed at the inner edge, replace the 12 with 1.5.
+23254 The formula for the circumferende of a circle is: C = π·d
At the outer edge: C = π·d = π·12 = 12π cm
A point on the outer edge travels 12π cm each revolutions, so, in 100 revolutions, it travels
100 times 12π = 1200π cm; so its speed is 1200π cm/min
If you want, you can turn this into a decimal equivalent.
To find the speed at the inner edge, replace the 12 with 1.5.
