How many pebbles on a regulation NCAA basketball?

Answer 1

According to the Spalding website, http://www.spalding.com/contact/contact.html#Q6, there are 122 pebbles per square inch on a Spalding Basketball which makes approximately 35,000 pebbles on a Spalding basketball. The curved surface area of cylinder = 2prh

Since we know that h (height) is equal to 2r we can write = 2pr(2r)

Simplify that and the surface area of a sphere with radius r = 4pr2

So let's try the size 7 basketball first. A solid sphere has a radius of 23.9 cm. To calculate its surface area we'll have to get the radius. A radius is half of the diameter.

r = 23.9 cm/2

r = 11.95cm

p = 22/7

Surface area = 4 pr2

= 4 x 22/7 x 11.95 x 11.95

= 1795.23 cm2

If there are 122 pebbles for every 6.45 cm2, then we just divide 1795.23 cm2/6.45 cm2 and we'll get the magic number you're looking for, or at least a pretty good estimate... There are about 278 pebbles on a regulation size 7 ball. Using the same method for the other two ball sizes I get, 258 pebbles for the size 6, and 235 pebbles for the size 5. Of course, to get the exact number we'd have to subtract the area used for the nipple, and the black grooves on the basketball.