Question

The ball of a ballpoint pen is 0.5 mm in diameter and has an ASTM grain size of 12. How many grains are there in the ball

Answer 1

Given :

The ball of a ballpoint pen is 0.5 mm in diameter and has an ASTM grain size of 12.

To Find :

How many grains are there in the ball?

Solution :

Volume of ball of the ballpoint is :

`V = (4 \pi r^3)/(3)\\\\V = (4* 3.14 * 0.5^3)/(3)\ mm^3\\\\V = 0.523\ mm^3`

Now, grain size of 12 has about 520000 grains/mm³.

Therefore, number of grains are :

`n = 520000* 0.523\ grains\\\\n = 271960\ grains`