Question

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.

Answer 1

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

Answer 2

Hi!Thanks for the answer. Might I ask what w represents?

Answer 3

w is Greek omega (I do not have Greek letters on my keyboard), the angular speed in radians per unit time.

Answer 4

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

Answer 5

Thanks again!:)