A golf ball has diameter equal to 4.1 cm. Its surface has 150 dimples each of radius 2 mm. Calculate totals area which is exposed to the surrounding assuming that the dimples are hemispherical.

Explanation

Let r be the radius of the golf ball `rArr=(4.1)/(2)`cm
If there is no dimple on the ball then,
Surface area of the ball =` 4pi(4.1/2)^(2) cm^(2)`
Oif 150 dimples are there then surface area equal to `150pi(0.2)^(2)` will be removed and surfcae area equal to `150pi(0.2)^(2)+150xx2pi(0.2)^(2)`
`=pi[16.81+150xx0.04]cm^(2)`
`=(22)/(7)(16.81+6)cm^(2)=(22)/(7)xx22.81 cm^(2)=71.69 cm^(2)`
Hence the surface area expose to the surrounding s is 71.69 `cm^(2)`(approx)