Posted by Willoby on Tuesday, January 4, 2011 at 3:41am.
A compact disk is 12 cm in diameter & rotates at 100 rpm 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 disk & the speed of a point on the inner edge.

Plane Trigonometry  Damon, Tuesday, January 4, 2011 at 4:54am
A revolution is 2 pi radians
So it goes w = 200 pi radians/minute
tangential speed = w r = r * 200 pi
at outside
v = 6*200 pi cm/min
at inside
v = 0.75 * 200 pi cm/min

Plane Trigonometry  Willoby, Tuesday, January 4, 2011 at 5:40am
Hi!Thanks for the answer. Might I ask what w represents?

Plane Trigonometry  Damon, Tuesday, January 4, 2011 at 5:44am
w is Greek omega (I do not have Greek letters on my keyboard), the angular speed in radians per unit time.

Plane Trigonometry  Damon, Tuesday, January 4, 2011 at 5:47am
If you have not studied that use:
Circumference at any radius = 2 pi r
Number of circumferences per minute = 100
so at any radius r
speed = 100 * 2 pi r = 200 pi r

Plane Trigonometry  Willoby, Tuesday, January 4, 2011 at 5:53am
Thanks again!:)
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